What is implied in the second paragraph？
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．
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．
What is true of robotic drivers？
A. It will take some time before robotic drivers can be put to practical use．
B. Robotic drivers are not allowed to drive on busy roads．
C. Robotic drivers can never replace human drivers．
D. Robotic drivers are too expensive to use．
靖在第_____处填上正确答案。
A. warn
B. suggest
C. invite
D. check
靖在第_____处填上正确答案。
A. at least
B. at most
C. at last
D. at best
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