What causes men and women to…——2014 高考英语第 48 题答案解析

【答案】B

【解析】考查细节理解。根据文章首段Women are friendly. But men are more competitive. Why?
Researchers have found it’s all down to the hormone
oxytocin(荷尔蒙催生素)可知，男女之间行为表现的不同是完全由于荷尔蒙催生素。