Question

It’s a difficult skill to master, but ______, it will benefit you for the rest of your life.

A．once obtained	B．when to obtain
C．after obtaining	D．while obtaining

Answer 1

A

试题分析：考查非谓语动词。句中的a difficult skill与obtain之间为被动关系，故用过去分词。句意：它是个很难掌握的技巧，但一旦被掌握，将对你的余生有好处。故A正确。