问题补充:
many times, but he still couldn understand it.
A. Having been told
B. Though he had been told
C. He had been told
D. Having told
答案:
A. Having been told
B. Though he had been told
(答案→)C. He had been told
D. Having told
解析:句中的but是连词,要连接两个相同的结构,本题中连接两个分句。