Mary has to study ____a math test A.at B.for C.in D.to
问题描述：
Mary has to study ____a math test A.at B.for C.in D.to
答
B.for 表目的,为月考而学习
Mary has to study ____a math test A.at B.for C.in D.to
B.for 表目的,为月考而学习