视网膜母细胞瘤的特点，错误的是（）

A.大多数为遗传性

B.遗传性患儿为Rb基因突变，突变基因位于13号染色体长臂1区4带

C.患儿可无症状或出现斜视、白瞳现象

D.典型的B超改变为"钙斑"

E.晚期可导致继发性青光眼、暴露性角膜炎并可全身转移

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.