—May I go and play with Dick this afternoon，Mum?
—No，you can’t go out________your work is being done.
| A．before | B．until | C．as | D．the moment |
His laziness ___________ his failing in the exam.
| A．result from | B．accounts for | C．because of | D．is on account of |
As we all know, smoking ___________ people’s health.
| A．is harmful to | B．do harm fo | C．does harmful to | D．harm |
_____ you have worked out the first problem, you may go on to work on the second.
| A．Even if | B．Unless | C．Now that | D．Though |
Most of the evidence was destroyed in the fire. _____, it would be almost impossible to prove Jim guilty.
| A．Anyhow | B．However | C．Besides | D．Thus |
_____ life exists on any other planet in the solar system still remains a question.
| A．Why | B．Whether | C．How | D．Where |