恳请各位NN解释一下这两题

102In the 1970's there was an oversupply of college grauates.The oversupply caused the average annual income of college graduates to fall to a level only 18 percent greater than that of wokers with only high school diplomas. By the late 1980's the average annual income of college graduates was 43 percent higher than that of workers with only high school diplomas, even though between the 1970's and late 1980's the supply of college graduates did not decrease.

Which of the following, if true in the late 1980's best reconciles the apparent discrepancy described above?

A)The economy slowed, thus creating a decreased demand for college graduates.

B)The quality of high school education improved.

C)Compared to the 1970's, a greater number of high schools offered vocational guidance programs for their students.

D)The proportion of the population with at least a college-level education increased.

E)There was for the frist time in 20 years an over-supply of job seekers with only high schools diplomas.

答案是E，想不通。高中文凭的人供不应求不正说明他们很紧俏吗，那他们的工资也应该有涨，那大学毕业生的工资怎么会还比高中毕业生的工资高那么多。

113Which of the following best completes the passage below?

The unemplyment rate in the United States fell from7.5 precent in 1981 to 6.9 precent in 1986. It cannot, however,be properly concluded from these statistics that the number of unemployed in 1986 was lower than it had been in 1981 because----

A)help-wanted advertisements increased between 1981 and 1986

B)many of the high-paying industrial jobs avail-able in 1981 were replaced by low-wage sevice jobs in 1986, resulting  in displacement of hundreds of thousands of workers.

C) in some midwestern industrial states, the unemployment rate was much higher in 1986 than it had been in 1981.

D)the total available work force, including those with and without emolyment, increased between 1981 and 1986

E) the average time that employees stay in any one job dropped during the period 1981 to 1986.

很显然，失业率降低不能说明失业人数减少，这更基数有关系。但是答案是E 不知道为什么。

以上两题是新东方蓝皮书的102和113题，室有迷惑，请各位NN看一看 答一答。。