问题补充：
, so he is afraid of dogs .
A. Having been bitten twice
B. Bitten twice
C. After he has been bitten twice
D. He has been bitten twice
答案：
A. Having been bitten twice
B. Bitten twice
C. After he has been bitten twice
(答案→)D. He has been bitten twice
解析：考察动词的非谓语形式辨析
句意为：他被狗咬过两次，所以很怕狗
从语法上看，该句式一个原因状语从句。前句应是一个完整的单句，故选D
考点:考察动词的非谓语形式辨析
