A.It is necessary for teens to join in sports and positive social activities.
B.Lack of adequate sleep puts teens at risk of performing poorly at school
C.Modern technology has something to do with teens' sleep problems.
D.Teens' sleep is linked to their relationship with people around them.

A.The harder
B.Hardest
C.Harder
D.The hardest

A.gave
B.gives
C.was giving
D.was given

A.does it
B.doesn't it
C.isn't it
D.is it

A.does it
B.doesn't it
C.isn't it
D.is it

A.A panel
B.uninterested judges
C.contestants
D.judged

A.woke up late
B.get much sleep
C.have been worrying
D.all night

A.he thought
B.ahead of
C.Some
D.because

A.he thought
B.ahead of
C.Some
D.because

A.Teens whose parents broke up can't sleep well.
B.Parents can help their children sleep better by restricting their use of technology.
C.Parents have nothing to do with their children's health habits.
D.Teens are unable to perform well at school if they don't get sufficient sleep.