This machine is very easy . Anyone can learn to use it in a few minutes.
A. operating
B. to be operating
C. operated
D. to operate
网友回答
A. operating
B. to be operating
C. operated
(答案→)D. to operate
解析：考查不定式的固定句型：句意：这个机器很容易操作，任何人几分钟就可以学会。使用了Sb/sth is+adj+to do这个句型，其中不定式要用主动表示被动，选D。