—Do you know where David is? I couldn’t find him anywhere.—Well. He _________have gone far—his coat’s still here. 

There was a lot of fun at yesterday’s party. You______come, but why didn’t you?

________ the present unemployment continue, the society would face a more troublesome situation.

(2012·全国卷Ⅰ)I ________ use a clock to wake me up because at six o'clock each morning the train comes by my house.

There was plenty of time.He       .