Robots____things that people can't,such as traveling to Mars.A.used to doingB.used to doC.are used to doD.are used to doing请说明原因,

Robots____things that people can't,such as traveling to Mars.A.used to doingB.used to doC.are used to doD.are used to doing请说明原因,
Robots____things that people can't,such as traveling to Mars.
A.used to doing
B.used to do
C.are used to do
D.are used to doing
请说明原因,

Robots____things that people can't,such as traveling to Mars.A.used to doingB.used to doC.are used to doD.are used to doing请说明原因,
C
句意是：机器人被用来做人类不能做的事,比如到火星旅行.
be used to do sth 被用来做...,可替换为be used for sth/doing sth
used to doing无此句式
used to do过去常常做……
be used to doing习惯做……