一道不难的题，就是看不懂答案

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

mark将ronald说的rates fall是price increase的必要条件,理解成rates fall是price increase的充分条件了,从而认为rates fall必然导致price increase.而ronald的意思是,没有rates fall,就不会有price increase.很拗口,希望能明白.

楼主解释得非常正确，我完全看明白了。

not A unless B结构，A是B的充分条件，B是A的必要条件，要A成立的话，没有B不行，光有B不够