It wasn’t until a month later I received his letter.A. thatB. sinceC. whenD. as

问题补充：

It wasn’t until a month later I received his letter.

A. that

B. since

C. when

D. as

答案：

(答案→)A. that

B. since

C. when

D. as

解析：：考查强调句型。本题是强调句型，是对not until a mouth later 进行强调，故A正确。句意：直到一个月后，我才收到一封信。故A正确。