Not believing their eyes, the visitors on the spot _______ the flying plane, doing some most difficult and dangerous tricks in the sky.

What’s the matter with the man hanging his headthere—Well，if you ________ know, hewas caught stealing my bike.

She finished the novel and returned it to me in time.

The thought of taking the exam again_____me, because I often felt____when I failed.

meet you outside the cinema in anhour, OK— ____