At the end of the year， he would return to China with happy memories of his experience on Boston and his students there — with all their questions.

At the end of the year， he would return to China with happy memories of his experience on Boston and his students there — with all their questions.
A.在结尾之后
B.在。。之后
C.在。。结束时
D.在结尾的结尾
正确答案：C