Have you ever practiced conversations with friends_____(improve)your speaking skills?

问题描述:

Have you ever practiced conversations with friends_____(improve)your speaking skills?
请问为什么不能填improving而是填to improve?

to do sth 表目的,做目的状语.
improving的话,动名词做定语,就像一个形容词,用作修饰前面的名词,显然这边不是.这边需要一个状语.所以要用to.