Where are my keys? I _____ lost them.
| A．oughtto | B．shouldhave | C．willhave | D．musthave |
---Thank God you’re safe!
--- I stepped back, just _______ to avoid the racing car.
| A．in time | B．in case | C．in need | D．in vain |
Not until I came home last night ________ to bed.
| A．Mum did go | B．did Mum go | C．went Mum | D．Mum went |
Work hard when young, ______ you will regret.
| A．and | B．so | C．but | D．or |
It’s hot in the shopping mall, because the air-conditioning system ______.
| A．broke up | B．broke down | C．broke in | D．broke out |
--- It’s the fourth time that heavy smog(雾霾) has hit the city this month.
--- It’s high time we _______ measures to fight air pollution.
| A．will take | B．took | C．to take | D．taking |