The key you have just got the front door.
A. is used to opening
B. is used to be opened
C. is used to being opened
D. is used to open
网友回答
A. is used to opening
B. is used to be opened
C. is used to being opened
(答案→)D. is used to open
解析：现在分词表示经常性发生的动作，不定式表示一次性的动作，根据题意你拿的这把钥匙只是用来开前门的，open 和door是主动结构，选D。