Adults can easily survive on seven to eight hours' sleep a night, (2)________ teenagers require nine or ten hours.

Read the following passage and choose the letter A, B, C, or D to indicate the correct word or phrase that best fits each of the numbered blanks. 

      Why is it that many teenagers have the energy to play computer games until late at night but can't find the energy to get out of bed in time for school? According to a new report, today's generation of children are in danger of getting so little sleep that they are putting their mental and physical health at (1)________. Adults can easily survive on seven to eight hours' sleep a night, (2)________ teenagers require nine or ten hours. According to medical experts, one in five youngsters gets anything between two and five hours' sleep a night less than their parents did at their age. 

      This raises serious questions about whether lack of sleep is affecting children's ability to concentrate at school. The connection between sleep deprivation and lapses in memory, impaired reaction time and poor concentration is well established. Research has shown that losing as little as half an hour's sleep a night can have profound (3)_________ on how children perform the next day. A good night's sleep is also crucial for teenagers because it is while they are asleep (4)________ they release a hormone that is essential for their 'growth spurt' (the period during teenage years when the body grows at a rapid rate). It's true that they can, (5)_______ some extent, catch up on sleep at weekends, but that won't help them when they are dropping off to sleep in class on a Friday afternoon. 

By Tim Falla and Paul A. Davies, Solutions Advanced. OUP

Choose letter A, B, C, or D to indicate the sentence that is closest in meaning to each of the following questions. 

The singer was _________ on the piano by her sister.

Experts in climatology and other scientists are becoming extreme concerned about the changes to our climate which are taking place.