I’m impressed with his determination. When he had a problem to solve he work at it until

问题补充：

I’m impressed with his determination. When he had a problem to solve, he work at it until he found an answer.

A. would

B. might

C. must

D. should

答案：

(答案→)A. would

B. might

C. must

D. should

解析：考查时态.句意:他的决心给了我深刻印象.当他有问题要解决时,他会致力于这个问题直到他找到答案.可知描述的是从过去某事时间点来看,将要发生的动作,故用过去将来时态,would为will过去时态,选A.