I couldn’t follow what he said , but at last I understand. A. for the firstB. at firstC. t

I couldn’t follow what he said , but at last I understand.
A. for the first
B. at first
C. the first
D. at the first

A. for the first(答案→)B. at firstC. the firstD. at the first解析：句意：一开始我听不懂他的话，但是最后我明白了。at first意为“一开始，最初”，for the first time意为“第一次”，均为介词短语在句中做状语；故选Ｂ。

这个答案应该是对的