Experts worry about airborne toxins that are emitted during some manufacturing processes because A.companies release millions of pounds of chemical wastes into the air each year. B.the effects of many of these substances are unknown. C.some airborne toxins are known to be cancer causers. D.microscopic particulates in the air are responsible for 150,000 deaths each year.
A.companies B. B.the C. C.some D. D.microscopic E.
【参考答案】
C 解析：该题目问及专家担心空气中毒素的原因。此段提到毒素是在某些生产过程中释放出来的，大大小小的公司每年向空气......