Read the passage and answer. Sleep is not a waste of time. During deep sleep the brain sorts and stores the information gathered during the day, which is why students who sleep well remember more of what they study. Lack of sleep, on the other hand, weakens concentration, slows reaction time and lowers the body's resistance to disease. Teenagers need about eight to ten hours of sleep a night, yet many get far less because of late-night phone use. Switching off screens an hour before bed is one of the simplest ways to sleep better. The writer suggests that many teenagers sleep too little because of:

1. noise
2. illness
3. heavy homework
4. late-night phone use

English MCQ · More English: Reading Comprehension MCQs · Practise