2. Complete the text with the past simple affirmative, negative or question forms of the verbs in brackets. Louis Pasteur 1822 – 1895

As a young man, Pasteur a) ......... (study) at the École Notmale in Paris. Then at the age of just 32 he b) ......... (become) a professor at the University of Lille. In 1856, Pasteur c) ......... (receive) a visit from a man called Bigo who d) ......... (own) a factory that e) ......... (make) alcohol from sugar beet. He f) ......... (have) a question for Pasteur: why g) ......... (the alcohol / turn / to acid?) When this h) ......... (happen), they i) ......... (not can) use it and j) ......... (throw) it away. Bigo k) ......... (ask) Pasteur to find out the reason for this. At first, Pasteur l) ......... (not know), but when he m) ......... (examine) the alcohol under a microscope, he n) ......... (find) thousands of many micro-organisms. He o) ......... (believe) that they p) ......... (cause) the problem. q) ......... (milk, wine and vinegar / behave / in the sane way?) Other scientists r) ......... (disagree) with him, and newspapers s) ......... (make) fun of him. However, Pasteur t) ......... (continue) with his work, he u) ......... (invent) methods of testing his theory and v) ......... (prove) that he was right. Later he w) ......... (work) together with two doctors and x) ......... (develop) vaccines for diseases such as anthrax and rabies.

3. 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 a) ......... warmer over the past 50 years, but they disagree about the causes. Some believe that human activities b) ......... climate change. They argue that for 1.000 or 2.000 years before 1850, when records c) ........., the temperature was more or less stable. Short warm or cold periods d) ......... during that time, but trhe climate always e) ......... to the same level. However, since the Industrial Revolution, human beings f) ......... more and more fissil fuels, such as coal and oil. In 1800 the atmosphere g) ......... around 280 parts per million of carbon dioxide (CO2). Since then there h) ......... an increase of about 31 %. This extra carbon dioxide i) ......... the world’s temperature because of the greenhouse effect.

Other scientists disagree that human activities over the past 50 years j) ......... global warming. They point out that volcanoes and other natural processes k) ......... CO2 into the atmosphere, and that human activity l) ......... a rise in CO2 of only three per cent.

In 1999, 156 countries m) ......... the Kyoto protocol, part of a United nations agreement on climate change, which n) ......... into force in 2005. They o) ......... to reduce their emissions of CO2 and other greenhouse gases, although so far, some countries, such as the USA and Australia, p) ......... any action.

1. A become 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.