547.Pleasant music is often played ______ classes to make students refreshed and relaxed for a while.

A.between

B.among

C.over

D.after

548.Although _______ my opinion,the old professor didn't come up with his own.

A.against

B.on

C.for

D.in

547.答案是A;

between用于两者之间，也可指多个事物每两者之间；among用于三者或三者以上。课间是指两节课之间，故选A。

548.答案是A;

against one'e opinion反对某人的见解；for one's opinion 同意某人的见解；in one's opinion 在某人看来。