[讨论]请教lsat-5-6-13

The only way that bookstores can profitably sell books at below-market prices is to get the books at a discount from publishers. Unless bookstores generate a high sales volume, however, they cannot get discounts from publishers. To generate such volume, bookstores must either cater to mass tastes or have exclusive access to a large specialized market, such as medical market, or both.

13.   Which one of the following can be properly inferred from the passage?

(A) If a bookstore receives discounts from publishers, it will profitably sell books at below-market prices.

(B) A bookstore that caters to mass tastes or has exclusive access to a large specialized market will have a high sales volume.

(C) A bookstore that profitably sells books at below-market prices gets discounts from publishers.

(D) A bookstore that does not sell books at below-market prices does not get discounts from publishers.（C）

(E) A bookstore that not only caters to mass tastes but also has exclusive access to a large specialized market cannot profitably sell books at below-market prices.

为什么选Ｃ啊？低价获利销售不是还有一种可能吗－较大的销售量

14.   If all statements in the passage are true and if it is also true that a bookstore does not cater to mass tastes, which one of the following CANNOT be true?

(A) The bookstore profitably sells some of its books at below-market prices.

(B) The bookstore does not profitably sell any of its books at below-market prices.

(C) Either the bookstore has exclusive access to a large specialized market or else it does not get a discount from any publishers.

(D) The bookstore does not have exclusive access to a large specialized market but profitably sells some of its books at below-market prices.（D）

(E) The bookstore does not have exclusive access to a large specialized market, nor does it get a discount from any publishers.

14题同一个题干，也犯傻，一块问了吧

你先找出关键词， 很多同一类的在这题里， 然后再看看是什么关系，什么条件。

还不明白的话， 我明天再回答你。

The only way that bookstores can profitably sell books at below-market prices is to get the books at a discount from publishers. Unless bookstores generate a high sales volume, however, they cannot get discounts from publishers. To generate such volume, bookstores must either cater to mass tastes or have exclusive access to a large specialized market, such as medical market, or both.

从出版商那获得优惠是低价赢利的必要条件。 销售量是获得优惠的必要条件。 或者迎合大众口味或者有专有的销售渠道（或两者）是销售量的必要条件。

根据必要条件原理。 A is the necessary condition for B. Then , if B ,  then A.

充分条件： （有之必然， 无之， 未必不然） 即一个结果有多种条件导致。有了某一条件， 必导致该结果。 可是有了该结果不一定能推出是哪种条件。

例如， 天下雨， 地就湿。 下雨是地湿的充分条件。 但撒水地也湿， 所以， 从地湿不能一定推出下雨。

必要条件： （无之必不然， 有之， 不必然）即一个条件可以导致多种结果。 有了某一结果， 就一定能推出该条件。

例如：狂做题， 水平见长。 狂做题是水平见长的必要条件。 有了水平见长， 就一定能推出你狂做题了。 但狂做题也可能导致水平不见长， 因为，如果只做不总结，做多少也白搭。

555 GG的逻辑理论真是好让人羡慕噢，谢谢你这么详细的解答。