it is important_______.A.to careful B.to careless C.careful D.to be careful

题目

it is important_______.A.to careful B.to careless C.careful D.to be careful

答案

选d, 考不定式作主语
it 是形式主语,不定式是真正的主语.
作主语的可以是名词,代词,不定式,动名词,不能是形容词,副词.
a, b,没有这种用法,c 是形容词,不能作主语.