mr smith likes watching his son swim in the pool 为什么是swim
问题描述：
mr smith likes watching his son swim in the pool 为什么是swim
答
watching 是感官动词,his son是宾语,用to swim必须省略to的这样的不定式短语作宾补,是语法的规定.除此之外,还可以用现在分词作宾补,表示动作正在发生着.