This machine is very easy . Anybody can learn to use it in a few minutes.
Aoperating
Bto be operating
Coperated
Dto operate
网友回答
A. operating
B. to be operating
C. operated
(答案→)D. to operate
解析：在句型“主语+be+adj+to do”中，如果这个主语是动词do的逻辑宾语，故用主动表被动，所以选D。
【考点】非谓语动词