If Concerns About Mad-Cow Disease Impose Economic Losses on the Perfectly

If concerns about mad-cow disease impose economic losses on the perfectly competitive cattle ranchers,exit by the ranchers combined with no further changes in the demand for beef will force the price of beef to

A) decrease.
B) not change.
C) increase.
D) fluctuate, with the trend being lower prices.
E) probably change, but more information about the market supply of beef is needed to answer the question.