For questions 1–8, read the text below anddecide which answer (A, B, C or D) best fits each gap. There is an example at the beginning. (0)
People spend about one-third of their lives asleep. lt seems certain, therefore, that sleep has a (0) ….VITAL….. function. However, what that function might be is still in (1) ………………………………. Scientists are far from being in agreement about (2) ……………………………… why so much of our precious time is given over to sleep.
There seem to be three main theories. The most popular states that the functions and (3) ……………………………. of sleep are primarily physiological. lt claims that we sleep in order to (4) ……………………………… the health of our body. In other words, biological processes work hard as we sleep to repair any damage done during the day and to restare ourselves to (5) ……………………………… efficiency. However, a second theory places more emphasis on the learning benefits of sleep. This theory holds that sleep allows us to process the information that we (6) ……………………………… during the day, and asserts that, without sleep, learning would not take place. A third popular theory is (7) ……………………………… on ideas about energy, saying that we need (8) ……………………………… of sleep in order to, in a sense, recharge our batteries and so have an adequate supply of energy for the coming day.