A、 Young children’s biological clock has the same rhythm with that of the teenagers．
B、 People after puberty begin to go to bed earlier due to the change of the biological clock．
C、 Children before puberty tend to fall asleep earlier at night than adolescents．
D、 Teenagers go to bed later than they used to due to the light from the computer screen．

A、 The human eye had two light—sensing systems．
B、 The human eye had one light—sensing system．
C、 The human eye could sense the light of day more quickly than the dark of night．
D、 The human eye could reset our internal clocks in accordance with the alarm clocks．