Research shows that though students benefit from having parents involved at school, happens at home matters much more.
A. which
B. what
C. that
D. whether
网友回答
A. which
(答案→)B. what
C. that
D. whether
解析：考查主语从句。本题的what引导起主语从句what happens at home，并在句中作主语。CD两项不能在句中做主语，which是指特定范围之内的某一个。故B正确。