Critical Reasoning

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