Some people fear that air pollution may bring about changes in weather around the world.

问题补充：

Some people fear that air pollution may bring about changes in weather around the world.

A. /; the

B. the; /

C. an; the

D. the; a

答案：

A. /; the

B. the; /

C. an; the

D. the; a

解析： Air pollution 是抽象名词这里是泛指，weather 这里是特指全球的气候，根据the weather around the world 可知。