The main purpose of Paragraph 2 is to ______.

A．answer an objection that some readers may raise to Paragraph 1

B．guard against the possibility that you have read Paragraph 1

C．contradict the idea of Paragraph 1

D．show more optimistic than Paragraph 1

（）是指撤消正强化物或者呈现负强化使得某一操作行为的概率下降。