Louis Pasteur 1822-1895

As a young man, Pasteur 1) studied at the École Nуrmale in Paris. Then at the age of just 32, he 2) (become) _______ a professor at the University of Lille. In 1856, Pasteur 3) (receive) _______ a visit from a man called Bigo who 4) (own) _______ a factory that 5) (make) _______ alcohol from sugar beet. He 6) (have) _______ a question for Pasteur: why 7) (the alcohol / turn / to acid?) _______ ? When this 8) (happen) _______, they 9) (not can) _______ use it and 10) (throw) _______ it away. Bigo 11) (ask) _______ Pasteur to find out the reason for this. At first, Pasteur 12) (not know) _______, but when he 13) (examine) _______ the alcohol under a microscope, he 14) (find) _______ thousands of tiny micro-organisms. He 15) (believe) _______ that they 16) (cause) _______ the problem. 17) (milk, wine and vinegar / behave / in the same way?) _______________________________? Other scientists 18) (disagree) _______ with him, and newspapers 19) (make) _______ fun of him. However, Pasteur 20) (continue) _______ with his work, he 21) (invent) _______ methods of testing his theory and 22) (prove) _______ that he was right. Later he 23) (work) _______ together with two doctors and 24) (develop) _______ vaccines for diseases such as anthrax and rabies.

10. 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 records 3) ___, the temperature was more or less stable. Short warm or cold periods 4) ___ during that time, but the climate always 5) ___ 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 activity 12) ___ a rise in CO2 of only three per cent.

In 1999, 156 countries 13) ___ the Kyoto protocol, part of a United Nations agreement on climate change, which 14) ___ 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