I am very sorry for ______ for so long.

I am very sorry for ______ for so long.
A、keep you waiting
B、having kept you waiting
C、waiting for you
D、keep you wait
【正确答案】：B
【题目解析】：介词后面要跟动名词做宾语，当动名词的动作在谓语动词所表示的动作之前发生时，要用动名词的完成式。例如：Thank you for having helped me so much. (感谢你给了我这么多的帮助。)本句的意思是：“很抱歉让你久等了。”