It seemed unlikely to me,but our class teacher seemed absolutely ___ about it.

题目

It seemed unlikely to me,but our class teacher seemed absolutely ___ about it.
A.sure B.positive C.certain D.doubtless
答案是B,请问为什么

答案

sure 的确,确定,当然
positive 确信的,明确的
certain 确实的,某一个
doubtless 无疑
其实这里 是 结构的问题
seem + 形容词,
seem 是联系动词,后面的形容词作表语,构成系表结构
其余都是副词