Many experts seem to agree that certain limit should be set on consumption of cars to ease

问题补充：

Many experts seem to agree that certain limit should be set on consumption of cars to ease air pollution.

A. a; the

B. /; the

C. the; /

D. the; a

答案：

(答案→)A. a; the

B. /; the

C. the; /

D. the; a

解析：第一个空，“一个必然的限制”是泛指，故用不定冠词a；第二个空，是特指，故用定冠词the。