Start studying early and don’t study too much.A. at one timeB. at a timeC. at timesD. from

问题补充：

Start studying early and don’t study too much.

A. at one time

B. at a time

C. at times

D. from time to time

答案：

A. at one time

(答案→)B. at a time

C. at times

D. from time to time

解析：at a time 一次；at one time曾经，一度。at times=from time to time有时候。