1.假装（要）去做某事
If you pretend to know what you don't know,you'll only make a fool of yourself.
不懂装懂就会闹笑话.
2.假装在做某事
Yet it needs,as a political matter,to pretendto be doing something.
但是,从政治方面来考虑,它还是需要装模作样,摆摆姿态.
3.假装已经做了某事
He pretended to have forgotten the conversation afte rthat night.
他假装已经忘记这个除夕所说的话.