16. 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.（B）

(E) Excess ozone and carbon monoxide require a minimum of two years to break down naturally in the atmosphere above a given area.

答案选B，Y

照理说免去了这些企业的环境污染控制的监视，这些企业将更为大制造气。

所以1988年的环境 应该更差。

感觉B对于解释污染天数在89年减少这一现象没有帮助，仪器更准

了，但是应用了吗？另外，即使应用了，也只能测得更多污染物，而89年污染少了，只能表明肯定另有它因！