To reduce the danger to life and property posed by major earthquakes, scientists have been investigating several techniques for giving advance warning of dangerous earthquakes. Since catfish swim erratically before earthquakes, some investigators have proposed monitoring catfish to predict dangerous earthquakes.

Which of the following, if true, most seriously undermines the usefulness of the proposal?

• AIn Japan, which is subject to frequent earthquakes, the behavior of catfish has long been associated with earthquakes.  
• BMechanical methods for detecting earthquakes have not proved effective.  
• CTremors lead to the release of hydrogen sulfide gas into water, thereby causing various fish and shellfish to behave erratically.  
• DCareful construction can reduce the dangers posed by earthquakes.  
• EEven very slight, fleeting tremors cause catfish to swim erratically.