______ has an internal clock that regulates the beating of our hearts, and the ______ of our breathing.
| A．Mankind; step | B．Human; pace | C．Human being; step | D．Man; pace |
Only by increasing the number of doctors by 50 percent ________ properly in this hospital.
| A．can be the patients treated |
| B．can the patients be treated |
| C．the patients can be treated |
| D．treated can be the patients |
Look! The ground is wet. It must have rained last night, ________？
| A．hasn't it | B．hadn't it |
| C．mustn't it | D．didn't it |
I told Mom that not everyone could manage to have 3 meals on time everyday, ________？
| A．could he | B．didn't I |
| C．didn't she | D．could they |
No sooner ________ down on bed ________ the telephone rang.
| A．had he lain; than | B．had he lied; when |
| C．did he lie; than | D．had he laid; before |
Honey, you ________ alcohol for they have stopped drinking.
| A．may not have bought | B．mustn't have bought |
| C．can't have bought | D．needn't have bought |