Start out right away, _____ you’ll miss the first train.
| A．and | B．but | C．or | D．while |
She would lend me the money if I promised to ________ within a month.
| A．bring it back | B．pay for it |
| C．pay it back | D．pay it out |
Water, _____ we cannot live, exists in the form of liquid, gas or solid.
| A．from which | B．on which | C．by which | D．without which |
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 |