scores of times but he still couldn’t understand it A. Having explainedB. Having been

问题补充：

scores of times , but he still couldn’t understand it ．

A. Having explained

B. Having been explained

C. Though it was explained

D. It was explained

答案：

A. Having explained

B. Having been explained

C. Though it was explained

(答案→)D. It was explained

解析：考查句子结构，两句话中间有but，说明是并列句，前面也是简单句，AB是分词，只能做非谓语，C是让步状语从句，选D，句意是：这已经被解释很多次了，但他还是没懂。选D，