In order to be for Christmas, all these gifts must be mailed immediately. A. at one time

In order to be for Christmas, all these gifts must be mailed immediately.
A. at one time
B. in time
C. at a time
D. in no time

A. at one time(答案→)B. in timeC. at a timeD. in no time解析：本题考查time短语。A. at one time曾经； B. in time及时； C. at a time每次几个； D. in no time立刻。句意：为了在圣诞节及时收到，所有这些礼物必须立刻寄出去。

我明天再问问老师，叫他解释下这个问题