选择题 If Peter had told his teacher about his difficulty in math homework , she _______ him before the exam.
【正确答案】 C
【答案解析】句意：如果皮特过去告诉他的老师他在数学作业方面的困难，她一定会在考试前帮助他。这是对过去的虚拟，从句用“if+主语＋had done”形式，主句用“主语＋would have done”的形式，故选C。