动词不定式to have seen怎么替换?

动词不定式to have seen怎么替换? 动词不定式1.She was often seen ____ in the room.A.dance B.to danc 动词不定式的完成式 to have done 表示什么? 动词不定式怎么用 动词不定式怎么用, 动词不定式包括to 例如：The only person I have ever known to have a ske 怎么区分哪些句子是不带to的动词不定式? 省to的动词不定式变被动该怎么变? 当句子是动词不定式完成时时,谓语动词是不带to的动词,后怎么接? 动词不定式 to的词性 动词不定式不加to to be about+动词不定式