Task 1 (12 points)
Read the text below and chose the word or phrase which best completes each sentence. An example (0) has been given.
Why do we need sleep? (0) [__The__] question still perplexes scientists, but there are now several (1) theories that explain our need for a daily nap. Some people need eight hours, while (2) can exist on four. But the (3) point is that everybody needs sleep: it is as essential as breathing and eating. Yet, (4) decades of study, scientists still do not know why we do it.
(5) , there are some curious clues and theories. One obvious clue is that we all feel better after a good night’s sleep, and much worse if (6) of a decent amount of sleep at night. In humans the need for sleep gets so strong after a few days that nothing will keep you (7) , with reports of people falling asleep standing up, even while (8) or having intolerably loud music (9) at them. Within days of having (10) sleep, people report confusion, (11) and hallucinations. (In case you are wondering, the world record for going without sleep is eleven days.) But (12) that we sleep because we are tired is rather like stating that we eat because we are hungry – it is why we sleep, but not necessarily why we need it.