---Do you know mother giant pandas have only one or two babies?----Sorry，I don’t knowA. a

---Do you know mother giant pandas have only one or two babies ?
----Sorry，I don’t know．
A. at a time
B. at time
C. at times
D. at that times

(答案→)A. at a timeB. at timeC. at times D. at that times解析：试题分析: 句意：你知道大熊猫妈妈一次只生一个或两个宝宝吗？对不起，我不知道。at a time一次，at time无此短语，at times有时，偶尔，at that times无此短语。giant pandas大熊猫，have分娩。根据语境可知是一次生一个或两个宝宝，故选A

这个解释是对的