Keys ( ) opening the lock in the door.

同学,为你

选择 D.are used for

知识点：
be used to doing 表示习惯于做某事
be used to do表示...被用来做某事
be used for doing 被用于做…

opening是ing形式的,因此选择be used for doing 被用于做…才是对的.好好看看区别.

例句：
be used to do--Knives are used to cut things.
be use for doing----Knives are used for cutting things




如果认可和满意我的回复,请点击【采纳为满意回答】按钮~、
手机提问的朋友在客户端上评价点【满意】即可.
~你的采纳是我前进的动力~~~