In a Weight Loss Study, Participants Who Swam for One

Multiple Choice

In a weight loss study, participants who swam for one hour daily lost less weight than those who ran for one hour everyday. This evidence supports the conclusion that running is a more effective exercise than swimming.
Which of the following, if true, most seriously weakens the argument above?

A) Several studies show that swimming is a highly effective cardiovascular exercise.
B) The participants who swam treated the swimming as a leisurely activity, as opposed to the runners who took the program seriously.
C) The calories expended from one hour of running or swimming are roughly the same for the average person.
D) Running is an easier activity to begin because it requires less equipment than swimming.
E) Several studies support the claim that both running and swimming are very effective for weight loss.