题目选项分析

In a review of 2,000 studies of human behavior that date back to the 1940s, two Swiss psychologists declared that since most of the studies had failed to control for variables such as social class and family size,, none could be taken seriously.

In a review of 2,000 studies of human behavior that date back to the 1940s, two Swiss psychologists declared that since most of the studies fail in controlling for such variables like social class and family size,, none could be taken seriously.