问题
选择题
At first I regretted _____ them to stay, but we soon became great friends.
A．to invite
B．invited
C．to have invited
D．inviting
答案
答案：D
题目分析：考查非谓语动词。句意：起初，我后悔让他们留下来，但是我们很快成了好朋友。regret doing sth表示后悔做了某事；regret to do sth遗憾（将要）做某事，根据句意可知，invite这个动作已经发生，regret后应该用动名词，排除A、B、C，故选D。