开学演讲稿高中英语热门20篇

However mean your life is, meet it and live it; do not shun it and call it

hard names. It is not as bad as you are.

It looks poorest when you are richest. The fault-finder will find faults in

paradise. Love your life, poor as it is.

You may perhaps have some pleasant, thrilling, glorious hours, even in a

poor-house. The setting sun is reflected from the windows of the alms-house as

brightly as from the rich mans abode; the snow melts before its door as early

in the spring. I do not see but a quiet mind may live as contentedly there, and

have as cheering thoughts, as in a palace.

自古，在文人的笔下，有“独怜幽草涧边生，上有黄鹂深树鸣。”的灵动;有“几处早莺争暖树，谁家新燕啄春泥”热闹;更有“芳树无人花自落，春山无人鸟空啼”的幽静。

路上，偶然发现学校的鸟竟将巢建在高高的地路灯上，先是为校园里这小生灵的加入而兴奋不已，环顾四周，整齐的广玉兰树上却没有一个鸟窝。诧异之余，仰首看在蓝天为背景的图上，高大路灯上孤独的鸟窝略显得有些凄清。

隔壁的小学中传来阵阵欢愉的声音：“春眠不觉晓，处处闻啼鸟。”是啊，春天在不知不觉中来了，可你还记得曾经的麦田，吹来阵阵稻香，鸟儿或在树上庇荫，或围着稻草人叽叽喳喳地叫个不停。扇着蒲扇乘凉的老人脸上绽开的菊花，眯着眼，轻轻的摇头细细地品味，那才是真正天籁之音啊!

记得小时候读过巴金的《鸟的天堂》，曾经是那样的羡慕。水中的小岛上，在高大的榕树环绕中，有很多的大的，小的鸟影。这样令人眼花缭乱，令人目不暇接。

现在，随着城市化进程的近一步加快，城市外围的进一步拓展，庄稼地变成了平整的马路，一片片树林变成了高楼大厦。人类永不满足的心侵蚀着越来越多的土地，地球正悄悄褪去它绿色的裙摆，突兀出的是她干瘪，僵硬的骨骼。试问，又有谁能受的了朝不保夕的生活，流离颠沛折磨够了它们，有一个能永久安家栖息的地方就满足了。

环境伦理学大师利奥波德曾哀伤地叹息道：“那些在年轻时曾被一阵活生生的风动摇的树仍然活着，但是十年后，只有最古老的栎树还记得这些鸟，而最后，只有沙丘认识它们。”城市里的树，是孤独的游魂，黯淡，寂寞，像乞丐般的将垂死的手伸向苍穹。鸟儿也只是躲躲藏藏的，听到一丝声音就会马上飞走。悄悄害怕，害怕可能很久以后，当最后一丝退去后，画家会对着一片高楼林立的建筑物发呆。而不知鸟是什么样子，不知树是什么颜色。

一声声鸟鸣划过城市的喧嚣，穿过绿草地，像山野间奔去。如果再不保护环境，最后的绿色可能只是在颜料的色盘上而不是眼里。随着更多科技的发明创再让人们的生活水平提高的同时也造成了空气的污染，青翠的树上蒙上了厚厚的灰尘，嬉笑的鸟在电线上眺望。人与自然和谐相处，不但是保护了动物，更是保护了我们自己。

夜静了，听见鸟在歌唱，那是在安抚树的灵魂的梵音，一曲亘古的歌谣，那样悠远，那样深刻。

Almost everyone wants to live a long life, but longevity is not for all

people. It is reported that most long life people are in villages, far away from

big cities. In village, life is closer to nature. The sky there is clear and

pretty; the air is fresh; the water is clean; and the food they eat are natural,

without any chemicals. Besides, those villages are abundant in green trees,

beautiful flowers, fresh fruit, and wild animals, which can evoke peoples

passions for life. Moreover, the living pace in those villages is rather slow.

People suffer less stress than cities’. Thus, they have more freedom to enjoy

what they like. No wonder that most villagers are strong and healthy. If I

become old someday, I would like to move to village to enjoy a more comfortable

and pleasant life.

因为喜欢才牵挂，因为牵挂才喜欢，牵挂是心的感受，牵挂包含着祝福欣赏，也有爱的成分，有相互的牵挂才会相互走进对方心里，有感动有默契，发自内心，来自灵犀，牵挂没有任何雕琢装饰，牵挂是浪漫，深沉，稳重，纯洁，牵挂没有绚丽却有爱慕情节，牵挂是甜中的苦涩，是苦涩中的甜蜜，在这个时候谁会说再见，没有，没有人会说再见。

牵挂是热情中的含蓄，让你心动，兴奋，是心心相印的知己，有爱的感悟，有爱的升华，有知足也有陶醉，是情感的寄托，牵挂是彼此欣赏，有默契有感动，牵挂是生活中的风景线，有阳光，有鸟语花香，有云，有雨，有明月，有清风，也包含着一丝丝忧郁，凄凉，失落，更美的是陶醉，这样的美有谁会愿意离开说声再见，没有，永远没有人会说再见。

牵挂是梦里的想往，是春天的鲜花是，夏日的凉风，是金秋的果实，牵挂是思绪里的飘飘雪花，是老酒琼浆玉液，是思绪的五彩祥云。

牵挂是醉人心扉的酒，是绽放的两朵心花，是夜里的珠泪，枕上的相思，使人夜不能寐，容颜消瘦，这是人间最珍贵的情感，这种情感是靠心灵来维系，牵挂是从心底升起的真诚情感，有谁会舍去这种情感，和情感说再见?因为我们是人，都有一颗心，谁也做不到。

因为这份浓郁的思念，有了这份牵挂，平淡岁月的幸福和满足，是美丽的风景，在延伸人生的旅途，有一个心灵伴侣，是精神上的欣慰。

The summer holiday is coming. Our class have had a discussion about what to do during the holiday. Some are in favor of staying at home. They think its both convenient and comfortable. Whats more, they can save money for other purposes. But they will lose the chance of getting to know the outside world.

However, others prefer to go out for traveling since it can increase their knowledge and broaden their horizons. But they will spend more money and meet some difficulties while traveling.

In my opinion, it would be much better to stay at home, for I can do what I like, such as reading books, watching TV, and helping my parents with the housework.

烟花绽彩，鼠去牛来，今日又回到了熟悉的校园，开学喽!校园中的一草一木又度过了一岁荣枯，相隔近月，虽然草疏木枯却亲切如故;熟悉的门窗、教室，还有那条小路，只是多了一层淡淡的尘土……。敬爱的老师们，亲爱的同学们，笑容洋溢，声声祝福，古人说：一日不见，如隔三秋，我们呢?办公室，教室里不断飞出欢声笑语??谈论着趣事，交流着收获，品评着新衣……的尘土……

旧的一年过去了，新的一年开始了，在新的一个学期里，我们应该做好每一项义务。叮铃铃!叮铃铃!……”随着一阵敲钟声，把玩野了的同学们带进了净化的学校。过了许久，我们班的同学们才到齐了。这是为什么呢?是有的同学不甘情愿，还是忘了这是敲钟声，还是……。老师在台上侃侃而谈，我们在下面静静的听。我觉得同学们不但不要打架骂人，还团结友爱，互相帮助，真像一个美满乐趣的大家庭.上课时，同学们认真听讲，积极发言，不懂就问，也没人拒人与千里之外.我感受到了欢乐，也替老师赶到欣慰，这难道不让我们感到亲切与舒服吗?发新书喽!”是我们班的大嗓门张刑飞在叫哦!班上的男同学争先恐后，班上的男同学争先恐后，我们在搬书的地方等了很久才搬到书，我拿了一摞书，真累。

或许，可以这样说，我的初一生活，无论在什么时候，在什么地方，都像灿烂的太阳一样明丽，会像天空翱翔的年轻的鹰一样豁达，像浩瀚的大海一样包罗万象。它会让我们一生受益------使我们充满朝气，充满自信，充满创造!使我们的人生变得靓丽多彩!

The Ten-minute Break Between Classes Time seems to be so limited for us Senior Three students. As a result, more and more students try to study from early morning till late afternoon, even during the ten-minute breaks. In my view, taking a ten minute break between classes is equally important. Otherwise, we will feel exhausted both physically and mentally,During the ten minute break, we are supposed to do something really relaxing, we need is to have a rest, instead of getting more tired. Besides, studying during the break doesn ’ t necessarily mean that you will achieve more. So doing nothing tiring in that short period is of greater significance. As far as my ten-minute breaks are concerned, sometimes I take some simple exercise, such as having a walk with my classmates, or just a free chat to refresh myself. When the next class begins, I feel energetic again.

成长的花儿，

人们只惊羡现时的名艳!

然而当初她的芽儿。

浸满了奋斗的泪泉，

洒满了牺牲的血雨。

——冰心

地球上的万物都有所追求，学生追求高考状元;科学家追求诺贝尔奖;运动员追求的是奥运会的金牌;树苗追求成为一颗屹立在风中的参天大树......只要是生物便会有一个追求，人们在追求中慢慢成长，追求的过程同样也是成长的过程。

小的时候，我总希望自己赶快长大，懂事后，便追求那种温文典雅的淑女风格，尽管他到现在还是我追求的目标，我生在一个较发达的国家，我不追求那种穷奢极欲的生活，我只希望我能吃得好，穿得好，睡得好，学得好。

首先，“吃”，当然啦，“人是铁，饭是钢，一顿不吃饿得慌。”我不希望我与孤儿院的孩子们，即使别人给献了爱心，也吃不饱NO，NO，NO，我所追求的生活不是这样。

其二，从孤儿院回来后，我的心久久不能平静，他们也是人啊!无论初夏秋冬，天气的冷热变化，也都只穿这么薄薄一件衣服吗?NO,NO,NO,我所追求的生活不是这样。

其三，今天，大家都去了孤儿院的宿舍，扑鼻而来的味道，让我胃里一阵翻江倒海，差点就吐了，试想，在这种条件下，孩子们每夜怎样入睡，NO,NO,NO,我所追求的生活不是这样。

最后一个，就是“学”，在孤儿院的小朋友里有哪一个受到正规的教育?想到这儿，心里不禁一酸，不争气的眼泪大滴大滴的滚落了下来。NO,NO,NO,我所追求的生活不是这样。

让我们在追求中成长，在成长中追求!

i am ****. usually a lot of my hobbies, such as skating, playing 356 didesmococcus feather, draw, watch extra-curricular book, watch tv and so on, so my life is very rich extra-curricular. ago is a more introverted person, i have very few words, only and i am very good friends to so many before, but after school at the time of my personality to change slowly, and not, as

previously like very few words, and students are also very harmonious relationship.

in fact, since childhood i dare not interested in english, so my english very poor, then let us hear english, introduce myself, i really do not know how to do, nervous for some time, so i think in the future of english class can have more understanding of english can have more interest in english. families are. usually a lot of my hobbies, such as skating, playing 356 didesmococcus feather, draw, watch extra-curricular book, watch tv and so on, so my life is very rich extra-curricular. ago is a more introverted person, i have very few words, only and i am very good friends to so many before, but

after school at the time of my personality to change slowly, and not, as previously like very few words, and students are also very harmonious relationship.

i think noting is difficult if you put your heart into it,so i can say will make my english be nice in future.

thank you!

[大学开学的自我介绍英语

1. a big headache令人头痛的事情

2. a fraction of 一部分

3. a matter of concern 焦点

4. a series of 一系列,一连串above all 首先,尤其是

5. absent from不在,缺席

6. abundant in富于

7. account for 解释

8. accuse sb. of sth.控告

9. add to增加(add up to)

10. after all 毕竟,究竟

11. agree with同意

12. ahead of time / schedule提前

13. ahead of 在...之前(ahead of time 提前)

14. alien to与...相反

15. all at once 突然,同时

16. all but 几乎;除了...都

17. all of a sudden 突然

18. all over again 再一次,重新

19. all over 遍及

20. all right 令人满意的;可以

21. all the same 仍然,照样的

22. all the time 一直,始终

23. angry with sb. at/about sth.生气,愤怒

24. anxious about/for忧虑,担心

25. anything but 根本不

26. apart from 除...外

27. appeal to 吸引，申诉，请求

28. applicable to适用于

29. apply to适用

30. appropriate for/to适当,合适

Today morning, I went to school. I have a little sad. Because my holiday was finish.

But when I walked into my classroom. I thought that I didn`t need to be sad. Because I saw all my classmate are very happy. But some of my classmate said:“We lost the free. ”

Then I saw my teacher came into the class. And she gave us the new books we need to use. And she told us what we must know in the new school term.

In the new school term, I will study hard!

Along with the time development accessing the net already turned the extremely universal matter. No matter is adult or the child so long as mentioning the computer all think of internet. But accessing the internet is advantageous but also has shortcoming.

I knew very many people access the net mainly is for playing games which is very bad for the study. Therefore some people believed the elementary and middle school students lack the self-control.

Butthere are many people approving to accessing internet why? Because internet can provide to the people very helps. First the network looks like a library we can look up very many materials easilyand it is quicker than the speed of consulting books; Next we may read a richer news on-line; In addition accessing the net also has other functions for example E-mail telephoning on the net and so on.

Actually accessing the net has its profit and the shortcoming place. We use it to open to expand the field of vision the study knowledge but must certainly grasp the discretion.随着时间的发展，接入网已经变成了极为普遍的问题。不管是大人还是孩子，只要一提电脑，都想到互联网。但是，上网是有利的，但也有缺点。

网络的好与坏高中英语作文 我知道很多人上网，主要是玩游戏，这对学习是很不好的。因此，有人认为，中小学生缺乏自我控制能力。

但是，有许多人赞成上网，为什么呢?因为互联网可以为人们提供很有帮助。首先，网络就像一个图书馆，我们可以看到很多材料很容易，而且比查阅书籍速度快;其次，我们可以读到更丰富的新闻在线;此外，上网还有其它作用，例如，电子邮件，网上通电话等等。

其实，上网有它的盈利和缺点的地方。我们用它来开阔视野，拓展视野，学习知识，但一定要把握自由裁量权。

Dear Li Hong,

I haven’t heard from you for quite a long time. How have you been these

days?

During the coming winter vacation, I’m going to Beijing for a tour. As I

have never been to Beijing before, I’d like you to be my guide. I hope you can

show me around the Great Wall, the Summer Palace and some other places of

interest. What’s more, during my visit I hope to stay together with you in your

house so that we can have a good talk about our life and studies. What do you

think of my idea? I would like to know your opinion.

Please give my best regards(问候) to your parents.

Yours sincerely,

Liu Ming

Teachers，good afternoon. Allow me to briefly talk about myself.

My name is - Xianning graduated from the south gate of the private secondary schools. Tourism now studying at the school in Hubei Province. Studying hotel management professional.

I was a character，cheerful girl，so my hobbies is extensive. Sporty. In my spare time likes playing basketball， table tennis，volleyball，skating. When a person like the Internet at home，or a personal stereo. Not like too long immersed in the world of books，and family members have told me，Laoyijiege is the best. Talking about my family，then I will talk about my family has. Only three people my family，my grandmother，grandfather and my own. My grandfather is a engineer，I am very severely on peacetime，the Church me a lot. Grandma is a very kindly for the elderly，care for my life in every possible way. Therefore，I have no parents in their care，childhood and growth were full of joy.

I like this hotel management professional，because I like to live in a strict order of the management environment. I have my professional self-confidence and hope，as long as the efforts will be fruitful，this is my motto. Since I chose this profession，I will follow this path，effort，perseverance path.

Thank you teachers. I finished presentation.

What is your favorite kind of music? Do you like jazz, popular music,

classical music, folk songs, blues, and so on? In high school I took one course

called music appreciation which I greatly enjoyed. This was not to learn how to

play a specific instrument but to learn how to read and listen to music as an

art form. We read the stories about the lives of many composers and the history

of the musical instruments themselves. Sometimes we listened to tapes at the

language laboratory, or concerts. Music is sometimes called a universal

language. A composer who cannot speak a single word of our language can make us

feel joy and pride, exaltation and despair, peace and mystery through his

music.

随着我们假期的结束，意味着我们又正式地踏入了校园。下面是小编为您带来的是开学中学英语日记相关内容，希望对您有所帮助。

Two months of summer vacation time has passed by, and we have ushered in a new school year. Now, I am a grade six primary school student, and should study hard to receive the next semesters entrance examination. Although my previous results are also good, but I think: the achievement in the past is past, does not mean the sixth grade now, we are standing on the same starting line, not Study hard how parents and teachers expectations?

School has been going on for a week, but I already feel the difference between grade six and grade five. It seems to have added a lot of weight to my shoulder. However, the new semester, I also met many new teachers, some of them are humorous, some very strict, some are full of meaning, some are uncertain......

Lets talk about the language teacher first! He is not only our Chinese teacher, but also our class teacher, called teacher yuan. Although Mr. Yuan is a bit tough, but he lectures very rich content, but also the management of our class there is no point, we all admire secretly ah!

The math teacher Lin is a kind and caring teacher, her class, told us very carefully, for fear of what is missing, we do not know as long as there is a problem, Lin teacher will give us again and again not to mind taking the trouble to explain, until we got so far.

And practice teacher, although has not made a self introduction, but she has left me a deep impression, on the first day of practice class, she told us many stories to my first impression is that the content is very rich.

Of course, our favorite teacher is Huang, who teaches music! She has a good sense of humor. When she is in the music class, lets play the game. The game lasts until the end of the class. During the game, just say a word (of course, you can answer the teachers question!) Listen to the students, and perform a program. Yong Xin even made 3 rules, not to mention the results, the performance of the program so that we can not afford to laugh up!

Of course, now we are in grade six, the elder brothers and sisters of grade 1~5 in the whole school. We should be a good example! I remember the four days of school, we do morning exercises in grade six, the national flag has been praised by the principals, teachers, I am in the heart ah, do not mention how happy!

The new term, the new beginning, the students, and strive to refuel, let us through the last year of primary school career!

[开学中学英语日记

我告别了难忘的小学生活，跨进了中学的大门。在这个金色的九月，带着几分新奇、几分梦想，我迎来了新的学期。

新环境、新同学、新任务、新集体，给了我新的憧憬。七五班，一个多么自豪、骄傲却又略带几分畏怯的名字，他是我人生路上一个新的起点。

初入新班级，我又高兴又感到孤单。高兴的是我走进了这个新的环境里读书、学习，孤单的是进入这个新的环境，认识的人很少。面对周围的陌生面孔，我心里有一种莫名的恐惧，总觉得自己不合群。可是我很快就被班级融化了，同学们的活泼天真、老师的和蔼可亲都像一缕缕春日的光辉洒在我的心房。

在这个温暖的大家庭中，我很快结识了许多新朋友，我们处的非常好。当然，我的老师也很好，我很喜欢他们。在老师和同学之间，不存在沟壑，大家彼此相交都很愉快。

我现在心中跳跃着阳光，浑身充满了力量。漫步于校园的小路上，尽情的呼吸着校园的空气，我真的很想喊几声来表示我满心的愉快。青春的活力与劲热在我胸中冲荡着，满怀着理想和期望的人生之帆即将扬起!在生命神圣海洋的航程中，我将劈风斩浪，勇往直前，寻找属于自己的天地!

风再大些吧!浪再猛些吧!电闪雷鸣都来吧!我会在那重重风浪中显示一个真实的自我、一个坚强的自我、一个不懈与斗争的自我!

When I was a child, I raised a pet, named Lucky.Actually he is a cat.His fur is soft with yellow and white color.Lucky is a good boy.He always behaves well.I remember when my uncle took him back to my home at first, I was afraid of him.But soon I found him is very interesting.I started to play with him.As time goes, we like each other very much.And then my uncle gave him to me.I was so happy.Now he always lies beside me quietly, when I’m doing my homework.As winter comes, he will sleep with me.sometimes he will dance for me, which is very funny and sometimes his hands are wet would leave many “plum flower” on the ground.He is so lovely.

在我还是个孩子的时候，就养了一只叫做幸运的宠物。其实他是一只猫。他的毛很柔软，是黄色和白色。幸运的是一个好男孩。他总是很听话。我记得当我叔叔带他来到我家的时候，我很怕他。但不久后，我发现他很有趣。我开始和他玩。随着时间的推移，我们都互相非常喜欢对方。之后我叔叔就把他送给了我。我是如此的高兴。现在他总是在我做家庭作业的时候悄悄地躺在我的身边。冬天来了，他会跟我一起睡。有时他会为我跳舞，那是非常有趣的，有时他的爪子湿了就会在地面上留下许多“梅花”。他很可爱。

Barack Obama who is the first black president in America will finish his last term of office soon. He is going to move away the White House and relieve his job as president. I still remember the time when Obama won the election and gave his inspiring speech, he said he wanted to make some changes to America.

Now 8 years have passed, his words have been tested.

Some people think he is a good president even though they don’t think what Obama brought to the country did not make a big difference.

But no one will deny that Obama is very humorous, it is known to all that he likes to watch the TV series. He keeps his eyes on them and sometimes he will play jokes in his personal Facebook. During his last term, he joined the talk show and showed his humor.

美国历史上第一位黑人总统巴拉克奥巴马很快就会完成他的最后任期。

他将离开白宫和卸下他作为总统的工作。我还记得当年奥巴马赢得大选, 发表了鼓舞人心的演讲,他说他想给给美国带来一些改变。

现在8年过去了,他的话会得到检验。有些人认为他是一个好总统,即使他们并不认为奥巴马给国家带来很大的影响。

但没有人会否认,奥巴马很幽默,众所周知,他喜欢看电视连续剧。他一直关注着美剧,有时他会在他的个人脸谱账号上玩笑。在他最后的任期里,他还参加了谈话节目,展示了他的幽默。

[高中英语作文：奥巴马的最后任职期限

高中写未来生活的英语作文带翻译范文篇1

With the development of science and technology, our lives have changed a lot in the past century. Many things that wouldn’t happen before have come into reality now. Therefore, our lives will change as well in the future. Our pace of live will greatly speed up, because we will help many machines to finish our work. Many things can be done autonomously. Therefore, people will have more time for fun. People can travel the outer space freely. Space shuttle can bring people to planets far from the earth. Human beings may live in other planets. Besides, our environment will be much better than now, because some effective measures are taken to protect the environment. Earth is still a beautiful home for human.

随着科技的发展，上个世纪我们的生活发生了很大改变。很多以前不可能发生的事现在都成为了现实。因此，我们将来的生活也会改变。我们的生活节奏会大大加快，因为我们会让很多机器帮我们完成工作。很多事情都可以自动完成。这样人们就有更多时间来玩了。人们可以自由到外太空旅游。航天飞机可以把人们带到远离地球的行星上。此外，我们的环境会比现在好，因为我们可以采取一些有效措施来保护环境。地球仍旧是人类的美好家园。

高中写未来生活的英语作文带翻译范文篇2

I imagine a lot about lives in the future. I think two words can summarize my imagination. The first word is fast. In the future, we will have more quickly transportation means. Now matter how far we go, it takes only a short time. With the development of science and technology, we can travel to the moon, Mars or somewhere outer space. People may can live in other planets. The second word is convenient. Because of the fast development of our society, many work can be done by the computers or even robots. Lots of things are fully automated. Humans just need to give some simple instructions to complete complecated tasks.

我对未来生活充满了想象。我认为可以用两个词来概括我的想象。第一个词是快速。将来，我们会拥有更快的交通方式。不管我们去得多远，它总能在短时间内把我们带到目的地。随着科学技术的发展，我们可以到月球，火星或者其他外太空旅游。人们也许可以在其他星球居住。第二个词是便利。由于社会的快速发展，很多工作可以用电脑或者机器人来完成。很多东西都是全自动的。人们只需要提供一些简单的指令来完成复杂的任务。

For this part, you are allowed 30 minutes to write a short essay based on the picture below.

You should start your essay with a brief account of the impact of the Internet on the way people communicate and then explain whether electronic communication can replace face-to-face contact. You should write at least 120 words but no more than 180 words.

“Dear Andy-How are youYour mother and I are fine .We both miss you and hope you are doing well. We look forward to seeing you again the next time your computer crashes and you come downstairs for something to eat, Love, Mom and Dad.”

范文: The modern technology has greatly altered the mode of

communication among people. With the help of the Internet, people can easily contact each other anytime anywhere. However, the side effect is that many people have become over-dependent on the Internet and neglected face-to-face communication.

As far as Im concerned, electronic communication cannot fully replace the direct contact among people. Although it seems to bring everyone together, it actually estranges people and decreases the effectiveness of communication. A typical example is that, traditionally, people working in the same office simply walk to others and talk. Today, however, co-workers tend to send e-mails or instant messages through the Internet even when they are sitting next to each other. As words can never convey the full message, it usually takes much more time and rounds of conversation than face-to-face communication, in which people can discuss more directly with less loss of information.

To conclude, the Internet enables more effective communication in some situations, but over-dependence on it actually pulls people apart.

[高中关于网络对人们日常交流影响的英语作文