Which of the following is effective topic sentence?

A.This paragraph will deal with the college library.

B.I am going to write about my job as a gas station attendant.

C.I do push-ups and sit-ups each morning.

D.Computers are changing our society.

E.Exercising every morning has had psitive effects on my health.

F.Using computers to teach school Children is a mistake.

正确答案：Exercising every morning has had psitive effects on my health.；Using computers to teach school Children is a mistake.