求助语法95-08-24

founder

95-08-24

A conductor [used ] signals and gestures to let the [musicians ] [to know ] when [to play] various parts of a composition.

答案是C ，为什么呢？let sb. (to) do ,"to"不是可要可不要吗？还有"when to play"没有语法错误吗？

挺困惑的！

fhhrewr

只有let sb do sth 是正确的，不可以加to。

when to play 是正确的。再举一个例子：In such a complicated situation, nobody knows what to do next.

founder

thanks a  lot !!