This building used to (be) a hotel.

题目

This building used to (be) a hotel.
用used to 句子中,什么情况下用used to be.像上面的话,为什么使用used to be,而不用used to has.

答案

因为这是个【主系表】句型,系动词是be(am is are)
看步骤：
This building was a hotel.
用used to + 动词原形以后：
This building used to (be) a hotel.
原因：be 动词的不定式形式就是to be