Do you hear my mother walking downstairs?为什么用该walking不用walk?hear sb do sth听见某人做过某事hear sb doing听见某人正在做某事这道题中应该是听见母亲下楼了,是做过了某事啊!

Do you hear my mother walking downstairs?为什么用该walking不用walk?
hear sb do sth听见某人做过某事
hear sb doing听见某人正在做某事
这道题中应该是听见母亲下楼了,是做过了某事啊!

意思是听见我妈妈正在下楼,不是下楼了,所以用ing