According to a 1980 survey, ten percent of all United States citizens over the age of sixteen are functionally illiterate. Therefore, if the projection that there will be 250 million United States citizens over sixteen in the year 2000 is correct, we project that 25 million of these citizens will be functionally illiterate.
Which of the following, if true, would most weaken the conclusion drawn by the author of the passage above

A．The percentage of high school graduates who do not go on to college has grown steadily over the past two decades.

B．From 1975 to 1980 there was a three-percent decrease in the rate of functional illiteracy among United States citizens over the age of sixteen.

C．Many United States citizens included in the 1980 survey would also be included in a survey conducted in the year 2000.

D．Surveys that are improperly designed usually provide inaccurate results.

E．(E) In 1980 sixty five percent of all United States citizens were over the age of sixteen.

ACARS系统是利用（）通信收发机传递数据的。

A、第一套VHF

B、第二套VHF

C、第一套HF

D、第三套VHF