Such problems______air pollution and traffic jams are becoming more and more serious in so

Cycling is a good exercise. ____, it doesn’t pollute the air. A. But B. Therefore C.

Professor James suggested that his students ______ a composition about air pollution.A．wri

As a defense against air－pollution damage, many plants and animals ______ a substance to a

______ at in this way, the air pollution in this region doesnt seem so serious.A．Having lo

The air pollution exceeds most ________ levels by 10 times or more.A acceptableB access

People in this area are in______over the heavily polluted air.A．doubtB．dangerC．troubleD．su