问题补充：
the party, we sang a song together.
A. In the end
B. At the end
C. In the end of
D. At the end of
答案：
A. In the end
B. At the end
C. In the end of
(答案→)D. At the end of
解析：A. In the end 最终，单独用，用逗号隔开 B. At the end 在终点 C. In the end of无此表达 D. At the end of在…结束时候，在末端；句意：在聚会的结束的时候，我们一起唱了一首歌。故选D
