请教关于not A unless B

NeTman · 发表于 2003-11-26 12:47:00

GMAT逻辑大全-GMAT-TEST B-17

Ronald: According to my analysis of the national economy, housing prices should not increase during the next six months unless interest rates drop significantly.
Mark: I disagree. One year ago, when interest rates last fell significantly, housing prices did not increase at all.
It can be inferred from the conversation above that Mark has interpreted Ronald’s statement to mean that
(A) housing prices will rise only if interest rates fall
(B) if interest rates fall, housing prices must rise
(C) interest rates and housing prices tend to rise and fall together
(D) interest rates are the only significant economic factor affecting housing prices
(E) interest rates are likely to fall significantly in the next six months

答案是B

根据公理:not A unless B是A->B,此中推出：house price increase->interest rate drop
可是house price increase->interest rate drop是答案B的逆命题,因此百思不得其解

请指点一二，谢过了先！

snow_mountain · 发表于 2003-11-26 15:31:00

你没有理解问题的意思。

ronald 的意思是，price increase 推出 interest rate drop

mark 的反驳却是，去年 interest rate drop 没导致 price increase. 很显然，mark's response is flawed. 假设，他的反驳是对的，那么，他对ronald 的话的理解就应该是， interest rate drop dao 导致了price increase. 就是答案B表达的。

请教关于not A unless B

请教关于not A unless B

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