We regret you that．because of the necessary repair, our library will be closed next month．
A. to inform
B. informing
C. to inform of
D. of informing
网友回答
(答案→)A. to inform
B. informing
C. to inform of
D. of informing
解析：句意：我很遗憾的告诉你因为必要的修理，我们的图书馆在下个月将被关闭。Regret作为“遗憾”的时候，后面接不定式做宾语，如果作为“后悔”讲，后面接动名词做宾语，所以选A。