while watching tv,___a.the doorbell rang b.we heard the doorbell ring c.we heard

题目

while watching tv,___a.the doorbell rang b.we heard the doorbell ring c.we heard
为什么选B啊?如果是D,那前面应该怎么说?为什么不是A呢?
c.we heard the doorbell rings d.we heard the doorbell rang

答案

while+v.ing的形式仅限于主句与从句的主语一致,watching TV的主语是we,主句的主语也应该是we
hear的用法是hear v.或hear v.ing
所以C D都不对