Although the pesticides used in nearby fields are the primary cause of

Although the pesticides used in nearby fields are the primary cause of pollution in the Ellenville River, researchers believe that increased automobile traffic c in the immediate vicinity is a contributing cause, since nearly all water samples taken from the river show signs of contamination from vehicular emissions. Such emissions are not typically considered a major source of water pollution, but researchers hypothesize that vehicular emissions are the source of more pollution in the Ellenville River than are pesticides.

Which of the following, if true, most strongly supports the researchers' hypothesis?

(A) Research has shown that there is more pollution from vehicular emissions in the Ellenville River than in any other river within a 500 miles radius.

(B) The water filtration system that produces drinking water for Ellenville is specifically designed to protect against the pesticides used in nearby fields.

(C) Water samples from the Ellenville River taken fifty years ago show evidence of pollution from vehicular emissions.

(D) In laboratories without the most sophisticated diagnostic tools, it is difficult to differentiate between types of water pollutants.

(E) The diseases caused by the different forms of water pollution cause different health problems, and the illnesses caused by vehicular emissions are much more prevalent in Ellenville than are those caused by pesticides.