Look at the trouble I am in now! If only I _____ your advice !
| A．followed | B．would follow |
| C．had followed | D．should follow |
Experts have been warning _____ of the health risks caused by passive smoking.
| A．at a time | B．at one time | C．for some time | D．for the time |
He was told that it would be at least three months ___ he could recover and return to work.
| A．when | B．before | C．since | D．that |
Scientists are convinced ___ the positive effect of laughter ___ physical and mental health.
| A．of; at | B．by; in | C．of; on | D．on; at |
We had to wait half an hour _______ we already booked a table.
| A．since | B．although | C．until | D．before |
Help others whenever you can ______ you will make the world a nicer place to live in.
| A．and | B．or | C．unless | D．but |