GWD7-Q30:
weaken
Printwell’s Ink Jet Division manufactures ink-jet printers and the ink cartridges they use.
Sales of its ink-jet printers have increased.
Monthly revenues from those sales, however, have not increased, because competition has forced Printwell to cut the prices of its printers.
Unfortunately, Printwell has been unable to bring down the cost of manufacturing a printer.
Thus, despite the increase in printer sales, the Ink Jet Division must be providing the company with much smaller than it used to.
Which of the following, if true, most seriously weakens the argument?
A [url=]Ink-jet printers in regular use frequently need new ink cartridges, and Printwell’s printers only accept Printwell’s ink cartridges.[/url] B [url=]Unlike some competing companies, Printwell sells all of its printers through retailers, and these retailers’ costs account for a sizable proportion of the printers’ ultimate retail price.
[/url]C Some printer manufacturers have been forced to reduce the sale price of their ink-jet printers even more than Printwell has.
D In the past year, no competing manufacturer of ink-jet printers has had as great an increase in unit sales of printers as Printwell has.
E In the past year, sales of Printwell’s ink-jet printers have increased more than sales of any other type of printer made by Printwell.
答案是Ａ，请教一下，大概怎么理解的，Ｂ呢，其它的怎么排除？ | 
