Tom's mother kept telling him that he should work harder, but ______didn't help．
A.heB.whichC.itD.one在线课程C
试题分析：句意：汤姆的妈妈一直告诉他他应该更加努力学习，但那没用。从题目中可以看出这是并列句，it指代Tom's mother kept telling him that he should work harder.整句话。所以选A。
考点: 考查代词的用法。