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Past Simple and Present Perfect
| Past Simple versus Present Perfect | |
| Past Simple | Present Perfect |
| complete action which happened at a time in the past: e.g. She left yesterday. (When did she leave? Yesterday.) | complete action which happened at a time in the past e.g. Don has left for Madrid. (We don't know when he left; unstated time; he's now there or on his way there.) |
| past action which is and happened at a definite past time not mentioned e.g. I met John Lennon. (I won't meet him again; he's dead. – period of time finished) | past action which is and happened at a definite past time not mentioned e.g. I' ve spoken to Richard Gere. (I may speak to him again; he's alive. – period of time not finished yet) |
10.1 Read the text about climate change. Choose the correct form, A or B, to complete the sentence:
At the moment, scientists agree that the world's climate 1) B warmer over the past 50 years, but they disagree about the causes. Some believe that human activities 2) ___ climate change. They argue that for 1,000 or 2,000 years before 1850, when records3) ___, the temperature was more or less stable. Short warm or cold periods 4) ___ during that time, but the climate always5) ___ to the same level. However, since the Industrial Revolution, human beings 6) ___ more and more fossil fuels, such as coal and oil. In 1800 the atmosphere 7) ___ around 280 parts per million of carbon dioxide (CO2). Since then there 8) ___ an increase of about 3 l%. This extra carbon dioxide 9) ___ the world's temperature because of the greenhouse effect.
Other scientists disagree that human activities over the past 50 years 10) ___ global warming. They point out that volcanoes and other
natural processes 11) ___ CO2 into the atmosphere, and that human activity12) ___ a rise in CO2 of only three per cent.
In 1999, 156 countries13) ___ the Kyoto protocol, part of a United Nations agreement on climate change, which14) ___ into force in 2005.They 15) ___ to reduce their emissions of CO2 and other greenhouse gases, although so far, some countries, such as the USA and
Australia,16) ___ any action.
1. A became B has become
2. A caused B have caused
3. A began B have begun
4. A occurred B have occurred
5. A returned B has returned
6. A burned B have burned
7. A contained B has contained
8. A was B has been
9. A raised B has raised
10. A caused B have caused
11. A always released B have always released
12. A contributed B has contributed
13. A signed B have signed
14. A came B has come
15. A agreed B have agreed
16. A did not take B have not taken
Present Perfect Continuous
Use
1) actions started in the past and continuing up to the present
He 's been writing a letter for two hours. (He started two hours ago and he's still writing it)
2) past actions of certain duration having visible results or effects in the present
She 's been crying. (Her eyes are red.)
3) actions expressing anger, irritation, annoyance, explanation or criticism
Who has been using my toothbrush? (annoyance)
4) emphasis on duration (usually with for, since or how long) She 's been calling on clients since this morning.
Time expressions: how long, for, since
Note: live, feel and work can be used either in the Present Perfect or the Present Perfect Cont. with no difference in meaning.
I’ve been living / I’ve livedin Rome for a year.
11.1 Complete the sentence using the verb in brackets in the present perfect continuous form:
1. I’m sorry to keep you waiting. I hope you (not wait) __________ long.
2. There you are! We (look for) __________ you all morning!
3. I feel really tired. I (study) __________ hard lately.
4. Anna has got a really good suntan. She (go) __________ to the beach a lot.
5. Tom needs cheering up. He (have) __________ a lot of problems lately.
6. I haven’t seen you for ages. What (you / do) __________?
7. I (work) __________ here for the past three years, and I really like it.
8. Sam and Chris (paint) __________ their room, and their clothes are covered in paint!
11.2* Underline the correct form:
A. Scientists 1) have recently identified / have been identifying a new species of animal in the rainforest of Borneo. They2) have been searching / searched for this creature for several years, after reports from local villagers, and say it is a type of lemur.
B. Archaeologists in Guatemala 3) have found / have been finding a Mayan wall painting which they think is more than 2,000 years old. Archaeologist William Saturno 4) explored / has been exploring the site since 2002.
C. Scientists using the Hubble Space Telescope think they5) found / have found two new moons circling the planet Pluto. Astronomers6) have been looking / looked closely at Pluto since 1978 when they 7) spotted / have spotted its first moon. The telescope8) worked / has been working for fifteen years, and 9) has been producing / has produced more than 700,000 images of the universe.
D. Australian scientists10) have been discovering / have discovered a new coral reef over 60 km long in the Gulf of Carpentaria by using satellites to spot the reefs in deep water. Recently divers11) have managed / have been managing to reach the reefs and take photographs.
Past Continuous
Use
1) action in the middle of happening at a stated past time
He was playing tennis at 4.30 yesterday.
2) past action in progress interrupted by another past action. The longer action is in the Past Continuous, the shorter action is in the Past Simple.
While I was getting dressed the bell rang.
3) two or more simultaneous past actions
While I was sunbathing, Tim was swimming.
or background description to events in a story
She was flying to Paris. The sun was shining...
Time expressions: while, when, as etc
12.1* Underline the correct form:
1. While he took / was taking a bath, Archimedes discovered / was discovering the principles of density and buoyancy.
2. When Edouard Benedictus, a French scientist, worked / was working in his laboratory, he dropped / was dropping a glass bottle which had some plastic inside – and invented / was inventing safety glass.
3. Columbus arrived / was arriving in America while he tried / was trying to reach the Far East.
4. Alexander Fleming discovered / was discovering penicillin by accident while he looked / was looking at some old experiments.
5. While Hiram Bingham climbed / was climbing in the mountains of Peru in 1911, he discovered / was discovering the lost city of Macchu Picchu.
6. While Isaac Newton sat / was sitting under an apple tree, an apple fell / was falling on hishead, and he understood / was understanding gravity.
7. While Dr Harry Coover tried / was trying to invent a newkind of plastic, he made / was making a very softsubstance which stuck / was sticking things together. It was Superglue.
8. While he observed / was observing the Moon throughhis telescope, Galileo realized / was realizing that it hadmountains and craters.
12.2* Complete the sentence with the past simple or past continuous form of the verb in brackets:
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