八年级英语下册知识讲义-语法讲解(现在完成时和其他时态的区分)-外研版

知识梳理They have been to many interesting places.他们去过很多有意思的地方。

我们在学习了现在完成时的相关知识后，最迫切想要掌握的就是对于已经学过的不同时态的一个区分。

在这里将一般过去时和现在完成时进行一个系统地区分还是很有必要的。

其余时态因为本身有着各自的侧重点，和现在完成时牵扯的关系不多，在这里我们只点到为止。

一般现在时只强调当前习惯性的动作，一般将来时的落脚点在将来。

现在进行时和过去进行时则更多强调某一时刻“正在发生”的动作。

一般过去时的主要侧重点在于描述“过去发生的动作”。

在时间上多强调“点”。

而现在完成时则主要强调动作的延续，在时间上多强调“段”。

I saw this film yesterday. 我昨天看了这部电影。

I have seen this film. 我已经看过这部电影。

这两句话中，前一句只强调昨天看电影的事实，而后一句则强调“已经看过”，说明以后可能不想再看。

1. Jay is my favourite star and I _________ to his concerts many times.A. wentB. goC. will goD. have been2. Sally's sister __________ in Beijing for more than 3 years. She loves living in Beijing.A. studiedB. have studiedC. has studiedD. is studying3. —Have you ever entered a competition?—No, never. But I ________ about it for a long time.A. dreamedB. dreamC. have dreamedD. will dream4. I have __________ visited the USA, but I'm sure some day I will.A. everB. neverC. alwaysD. already5. I don't want to see the film because I __________ it already.A. sawB. have seenC. seeD. will see答案：DCCBB思路分析：时态的复习。

【即学即练】1. We __________ our little dog in the garden, so we are very happy now.A. have foundB. foundC. findD. will find2. Lucy is in London now. She ________ several emails to us recently.A. sentB. sendsC. will sendD. has sent3. My aunt _______ in Beijing. I'm going to see her.A. arrivedB. has arrivedC. arrivesD. will arrive4. —Have the students finished their homework ___________?—Yes, they have.A. justB. alreadyC. yetD. ever5. She isn't in the classroom now because she _________ the library.A. has been toB. have been toC. have gone toD. has gone to6. Tom and Tony ________ the interesting story-book several times.A. readB. are readingC. readsD. have read7. We ________ that our spacecraft has landed on Mars.A. were hearingB. heardC. have heardD. will heard8. Mike and his parents have ________ gone to Hong Kong. They'll return in a week.A. yetB. alreadyC. neverD. ever9. Lots of astronauts _________ to the space station. They found it very interesting.A. has beenB. have beenC. have goneD. has gone10. The students _________ their summer holiday plans already.A. makeB. madeC. have madeD. will made11. Scientists have _________ discovered many other galaxies in the universe.A. yetB. alreadyC. neverD. ever12. Daming _________ his homework yet, so he can't play with his friends.A. doesn't finishB. won't finishC. hasn't finishedD. didn't finish答案：ADBCD DCBBC BC思路分析：考查时态和其他重点知识点。

同步练习一、完成句子。

1. 我参加过演讲比赛。

_______________________ a speech competition.2. —你的笔友以前来过中国吗？—没有。

—_____________________________ China before?—No, she hasn't.3. 我妈妈曾经看过这部电影。

___________________________ the film.4. —你曾想环游世界吗？—是的。

—_____________________________ around the world?—Yes , I have.5. 我们英语老师坐飞机去过很多地方。

Our English teacher ____________________________.二、阅读理解。

（A）Are you aged between 14 and 19 years old? Do you care about your local environment? Would you like to help make the area you live in better, cleaner, safer and more friendly?If your answers are “yes”, “yes” and “yes”, then read on! You may be surprised to hear that you can actually get money for improving your local community.The “Big Lottery”is giving money to groups of teenagers who want to become active citizens. We have ￡80,000 to distribute. We’re looking for young people to take part in schemes and projects near to where they live.Here are a few easy things you could do to get started.Meeting the neighboursEverybody needs good neighbours. Knock on people’s doors and find out what they would like to make your area better. Set a date for a meeting and then make some plans together. If you don’t want to go round to their houses, then you could always put a note through their doors.Neighbourhood watchNeighbourhood watch schemes are very popular in the UK. If you go away on holiday and leave your house, it’s very nice to know that a neighbour is keeping an eye on it. It’s a good way to make the area you live in safer. You could set one up easily and quickly.Lending a handThere are often elderly people living in the neighbourhood who may not be able to do the things that you can. Offer to do their shopping once a week, look after their garden for them or maybe walk their dog!No litteringNobody likes picking up other people’s rubbish, but a clean street can make all the difference. Take it in turns to go out once or twice a week and see what you can find something valuable.RecyclingNearly two-thirds of your rubbish can be recycled. Some areas already provide places for people to recycle bottles, tins, plastic and paper. Find out if this is done in your neighborhood. If it’s not, do something about it.So, go on… Help make your neighborhood ‘streets ahead’. Just tell us what kind of project you want to become involved in. Then we’ll send you more details. Take positive action and help make your neighborhood a better place to live in!1. The underlined word “distribute” means __________.A. give outB. get awayC. check outD. pay back2. From the passage we can know ___________.A. all the teenagers in the neighbourhood are needed to join the projectB. we need to watch our neighbour carefully to make our houses safeC. we can discuss plans with our neighbours to make our area betterD. we should shake our hands with old people in the neighbourhood3. The author advised the teenagers to take part in the project in order to ____________.A. make the area they live in safer and more friendlyB. improve the environment of the local communityC. help the old people and teenagers in the communityD. help to pick the rubbish in the street and recycle it（B）Riding in school buses in the early morning, then sitting in poorly lit classrooms, are the main reasons students have trouble getting to sleep at night, according to new research.Teenagers, like everyone else, need bright light in the morning to allow their circadian rhythms（生理节奏）to get into step with nature’s cycles of day and night.If they don’t get blue light in the morning, they get to sleep an average of six minutes later at night, until their bodies are completely out of sync（同步）with the school day, researchers from Rensselaer Polytechnic Institute in New York said last month.The finding was made by fitting goggles that block blue light from the sun to a group and of students. The researchers discovered that their circadian rhythms were greatly affected.Parents and teachers have been complaining in recent years that teens stay up too late at night, then fall asleep in class the next morning and do poorly in school. The new findings provide a possible explanation for the problem.At the root of the research is the circadian rhythm, the body’s natural sleep waking cycle. Even though the Earth makes a full rotation（旋转）in 24 hours, the body’s circadian cycle is about 24 hours and six minutes long. The cycle is mediated（调节）by a chemical called melatonin（褪黑激素）. The body starts to produce it about two hours before it is time to sleep and, in the absence of blue light, the body produces about six minutes later each day.In the study, the researchers studied 11 students at Smith Middle School in New York, which was designed so that a lot of sunlight reaches classrooms. On a Friday night, the researchers measured what time the 11 students’ bodies began releasing melatonin. On Monday morning, the students were sent to school with orange goggles that blocked most blue light from their eyes to mimic（模拟）the conditions found in many – if not most – schools. By the end of the week, the students were releasing melatonin 30 minutes later in the evening – an average of six minutes a day – and going to sleep later.“This is our first field study,” said lead author Mariana G. Figueiro. He said they would like to repeat it in larger studies and for longer periods of time. If the findings are repeated, a variety of solutions are available. Ideally, new schools would be built to allow more natural sunlight into the classrooms. Students could also be exposed to more sunlight outside.1. According to the findings related in this article, many teenagers stay up late because ______.A. they lack melatonin in their bodiesB. they have a lot of homework to doC. they get up so early to catch the busD. their circadian rhythms are in disorder2. What does the underlined sentence in the last paragraph mean?A. If we repeat the findings, many solutions to the problems will be used.B. If the findings appear again, different solutions could be found easily.C. If the findings proved to be correct, all kind of solutions could be found.D. If we repeat the studies, we can find many ways to solve the problems.3. What can we infer from the passage that ______.A. few schools have small windows and the classrooms are poorly litB. the sunlight is the only thing that can affect our circadian rhythmsC. the fitting goggles can help the teenagers to solve the sleeping problemsD. students who get more blue light are less likely to have sleeping problems4. The passage is mainly about ________________.A. the causes of teenagers’ disordered circadian rhythmsB. the new research on the teenagers’ sleeping problemsC. the ways of improving the condition of the classroomsD. the study on helping the teenagers not fall asleep in class答案一、1. I have entered2. Has your pen friend ever come to3. My mother has ever seen4. Have you ever wanted to travel5. has been to many places by plane二、（A）ACB（B）DCDB。