Air pollution is getting more and more serious, so we must take action __________ it is too late.
| A．before | B．after |
| C．until | D．when |
—Shall we go out for a walk?
—Sorry. This is not the right ____ to invite me. I am too tired to walk.
| A．moment | B．situation | C．place | D．chance |
I bought a dress for only 10 dollars in a sale; it was a real______.
| A．exchange | B．bargain | C．trade | D．business |
Most air pollution is caused by the burning of ____ like coal, gas and oil.
| A．fuels | B．articles | C．goods | D．products |
What’s the _____ of having a public open space where you can’t eat, drink or even simply hang out for a while?
| A．sense | B．matter | C．case | D．opinion |
The journey around the world took the old sailor nine months, _____ the sailing time was 226 days.
| A．of which | B．during which | C．from which | D．for which |