Question

动词填空I said you ____(work)harder if you wanted to pass the exam.请告知理由

Answer 1

would / should /must / had to work 。
一、英语中，一般来说，从句的时态要服从主句的时态，主句是过去时，从句也应该是与过去相关的时态；二、条件从句用了wanted 是过去时，三、因为包含条件从句，少不了要用到情态动词。