Question

They had finished the work ________ last month．

1. A.
   in the end of
2. B.
   at the end of
3. C.
   by the end of
4. D.
   in the end

Answer 1

C
详解：by the end of接过去时间点时，用过去完成时。从had finished过去完成时态可断定答案为C项。
讲台挥洒一刻：
at the end of, by the end of与in the end
①at the end of意为“在……末/尽头”，后面既可跟时间名词，又可跟地点名词，还可跟抽象名词。
You are going on holiday at the end of this month, aren't you?
你这个月底要去度假，是不是？
Go straight ahead and you'll find his house at the end of the street．
一直往前走，在这条街的尽头你会找到他家。
He is at the end of his patience．
他已经忍耐到了极限。
②by the end of…意为“到……末为止”或“在……末之前”。
by the end of 接过去时间点时，用过去完成时；接将来时间点时，用将来完成时。
We had learned 18 English songs by the end of last year．
到去年年底为止我们学了18首英文歌曲。
③in the end意为“最后，终于”，后面不跟of。
In the end, we decided not to buy it．
最后我们决定不买它。