As a rule, you can borrow only two books in the library.
A. at one time
B. at a time
C. in no time
D. at times
网友回答
A. at one time
(答案→)B. at a time
C. in no time
D. at times
解析：“作为一个规定，一次你只能从图书馆借一本书。”at one time“曾经”，at a time”一次”，in no time“立刻”，at times“有时候”，所以答案B。