he___ be in the classroom,i think.no,he ___ be in the classroom.i saw him go home a miute ago.,

题目

he___ be in the classroom,i think.no,he ___ be in the classroom.i saw him go home a miute ago.,
A.can;may not B.must ;may not C.may;can`t D.may;mustn`t请问应该选哪个,为什么?

答案

C 第一空‘ 可能’（不大确定时用；而MUST 表示‘肯定的猜测’ ；‘ 第二空是否定句中的猜测只能用can't .