Animal studies show that ______

单选题Animal studies show that _______.

[分析]细节题型
见第二段：动物研究表明具体的行为中可能存在一种生物因素；一些母猴惩戒雄性幼猴要比雌性幼猴早且频繁，同时它们触摸雌性幼猴的次数也比雄性的多，它们对雌性幼猴的保护也更强。因此D为答案。

1According to Helen, the word "passivity" underlined in Paragraph 3 means ________.

2Which of the following is NOT true of the study of hormones?

3Scientists think that __________.