In 1986, the city of Los Diablos had 20 days on which air pollution reached
unhealthful amounts and a smog alert was put into effect. In early 1987, new
air pollution control measures were enacted, but the city had smog alerts on
31 days that year and on 39 days the following year. In 1989, however, the
number of smog alerts in Los Diablos dropped to sixteen. The main air
pollutants in Los Diablos are ozone and carbon monoxide, and since 1986 the
levels of both have been monitored by gas spectrography.
Which of the following statements, assuming that each is true, would be LEAST
helpful in explaining the air pollution levels in Los Diablos between 1986
and 1989?
(A) The 1987 air pollution control measures enacted in Los Diablos were put
into effect in November of 1988.
(B) In December of 1988 a new and far more accurate gas spectrometer was
invented.
(C) In February of 1989, the Pollution Control Board of Los Diablos revised the
scale used to determine the amount of air pollution considered unhealthful.
(D) In 1988 the mayor of Los Diablos was found to have accepted large campaign
donations from local industries and to have exempted those same industries
from air pollution control measures.
(E) Excess ozone and carbon monoxide require a minimum of two years to break
down naturally in the atmosphere above a given area.
正确答案是(B)
是否因为新发明的gas spectrometer应该使1988和1989年的pollution levels都下降?
另外,答案选项(D)似乎也可以是答案
因为(D)所描述的"污染免列"是发生在1988年
如同正确选项(B)
(D)也无法解释为何1988年pollution levels没有下降,不是吗?
请前辈给予一些指点
谢谢! | 
