or because whereas so

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 (1) ________ for school? According to a new report, today's generation of children are in danger of getting so (2)_______ sleep that they are putting their mental and physical health at (3)_______. Adults can easily survive on seven to eight hours' sleep a night, (4)_______teenagers require nine or ten hours. According to medical experts, one in five youngsters (5)________ anything between two and five hours' sleep a night less than their parents did at their age.

Điền vào số 4