I.think ____ necessary for students.to take an interest in all subject.

问题描述:

I.think ____ necessary for students.to take an interest in all subject.
A.that.B.this
C.it.D.one.
求详解

C
I (主语) think (谓语)__it(形式宾语)__ necessary (宾补)for students.to take an interest in all subject(不定式的复合结构作真正宾语)
只有it 能作形式宾语,其它不用考虑.