Question

6. He pretended        when his father came in. (do)

当他爸爸进来时，他装作正在做作业。

Answer 1

6. to be doing his homework/that he was doing his homework pretend后应跟不定式，不可跟动名词，此处用不定式的进行时,表示动作在那时正在发生；亦可用从句形式。