Only by shouting at the top of his voice was he able to make himself heard. Only in this way can we achieve what we want.Only in each afternoon does the university library open. Only under special circumstances ____to take make?up tests. (CET-4 1997,6)

A) are freshmen permitted
B) permitted are freshmen
C) freshmen are permitted
D) are permitted freshmen

Only加状语位于句首,句子用倒装语序,故答案为A。
以only引导状语位于句首引起的倒装: http://insuns.com/article/15386-1.html