The information given by the lie detector, according to the author, is ______.

A．there are a lot of obstacles on the way ahead of human beings
B．human beings are surrounded by piles of rubbish
C．we are convinced that men are born evil
D．man's future is seen to be better advantaged from his good nature

A．physiological changes will for sure betray a liar
B．the bigger a lie is, the stronger the strain will be
C．the degree of the strain depends on the purpose of lying
D．a well-trained person can tell lies without being detected