【英语】He traveled to many mountain villages and saw many……

【英语】He traveled to many mountain villages and saw many……
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
为什么答案是C不是A?同样是过去时,同样是表示将会发生的,为什么A就不行?