题目如下：
He traveled to many mountain villages and saw many poor children out of school. This experience _______ his life.
A.would change
B.had changed
C.was to change
D.was changing
答案是C
请教老师，这里would change,was to change 和was changing有什么区别
He traveled to many mountain villages and saw many poor children out of school. This experience _______ his life.
A. would change
B. had changed
C. was to change
D. was changing
我觉得，此题只能选择一个最好答案，而没办法选一个正确答案。除去had changed 不能外，其余3 个都正确。理由：
A. would change （说话者的推断，would 表示“可能性”）
B. had changed（排除此答案，不可能早于前句发生）
C. was to change（过去以后时的一种。表示推断“注定要”）
D. was changing（traveled 和saw 这两个动作，是个反复的过程，不是瞬间结束。所以，was changing 表示，在过去某个时候就开始在改变着他的生活。）
