请教几道想不通的逻辑题

Before the printing press, books could be purchased only
in expensive manuscript copies. The printing press produced books that were
significantly less expensive than the manuscript editions. The public’s demand
for printed books in the first years after the invention of the printing press
was many times greater than demand had been for manuscript copies. This
increase demonstrates that there was a dramatic jump in the number of people
who learned how to read in the years after publishers first started producing
books on the printing press.

Which one of the following statements, if true, casts doubt
on the argument?

(A) During the first years after
the invention of the printing press, letter writing by people who wrote without
the assistance of scribes or clerks exhibited a dramatic increase.

(B) Books produced on the
printing press are often found with written comments in the margins in the
handwriting of the people who owned the books.

(C) In the first years after the
printing press was invented, printed books were purchased primarily by people
who had always bought and read expensive manuscripts but could afford a greater
number of printed books for the same money.

(D) Books that were printed on
the printing press in the first years after its invention often circulated
among friends in informal reading clubs or libraries.（C）

(E) The first printed books
published after the invention of the printing press would have been useless to
illiterate people, since the books had virtually no illustrations.

答案是C可是我觉得D也起到了削弱的作用啊。为什么是C而不是D呢？

Nutritionists have recommended
that people eat more fiber. Advertisements for a new fiber-supplement pill
state only that it contains “44 percent fiber”.

The advertising claim is misleading
in its selection of information on which to focus if which one of the following
is true?

(A)
There are other products on the market that are advertised as providing fiber
as a dietary supplement.

(B)
Nutritionists base their recommendation on medical findings that dietary fiber
protects against some kinds of cancer.

(C) It
is possible to become addicted to some kinds of advertised pills, such as
sleeping pills and painkillers.

(D) The
label of the advertised product recommends taking 3 pills every day.（E）

第一题，我没看出D削弱在哪里...原文中：

“This increase demonstrates that there was a dramatic jump in the number of people who learned how to read in the years after publishers first started producing books on the printing press.”

C对是一个很好的削弱，指出新增买书的人是那些本来就会Read之人，特别是C中有个“primarily”，指出大多数书是被本来就会Read的人买的

D只说了那些书经常流传在会读书的人之间，但是可以有这样一种例外，虽然符合D的意思，但实际上对原文产生了加强的作用：“书经常流传于会读书的人之间， 导致一大群会读书的人只需要相对较少的书的数量即可满足阅读需求，其他增加的销量还是有可能被那些刚刚学会Read之人买走”

相比之下，C中有了“primarily”之后，削弱的逻辑严密性就要高于D

第二题，请看清题目问得内容：“
            is misleading in its selection of information on which to focus ”

题目是让你分析在选择“Selection of information on which to focus”，多想想很快就有结论了！