she couldn't understand was fewer and fewer students showed interest in her lessons.
A. What ; why
B. That ; what
C. What ; because
D. Why; that
网友回答
(答案→)A. What ; why
B. That ; what
C. What ; because
D. Why; that
解析：句意：她不能理解的是越来越少的学生为什么对于她的课不感兴趣。第一空是what引导的主语从句，它在从句中作宾语，that不能在主句中作成分，why不能作宾语，故排除BD；第二空是why引导的表语从句，它在从句中作状语，根据句意故选A。