there's nothing for them to do but ____ silence.请问这空是填to remain 还是remain,各个感觉应该是填remain,因为前面有实义动词的do,后面不是应该省略to吗,但是答案是to remain.There is nothing left to him but to hit back.此句我能理解试比较：There is nothing left for him to do but hit back.而此句跟各位给出的there's nothing for them to do but to remain,到底应该用哪个呢？

there's nothing for them to do but ____ silence.
请问这空是填to remain 还是remain,各个感觉应该是填remain,因为前面有实义动词的do,后面不是应该省略to吗,但是答案是to remain.
There is nothing left to him but to hit back.此句我能理解
试比较：There is nothing left for him to do but hit back.而此句跟各位给出的there's nothing for them to do but to remain,到底应该用哪个呢？