As more and more cars are produced and used, so the from their exhaust-pipes contains an even larger volume of poisonous gas.
A. exposure
B. distribution
C. expansion
D. emission
网友回答
A. exposure
B. distribution
C. expansion
(答案→)D. emission
解析： emission散发物，发射。exposure(to)暴露于：They believe that their health problems are the result of years of exposure to fine cotton dust.(他们认为，他们的健康问题是多年来暴露于棉花粉尘所致。)expansion膨胀，扩大；Heat causes the expansion of gas.本题译文：正如汽车的生产和使用越来越多一样，汽车的排气管的散发物内所含的有毒气体量也在增加。