GMAT Critical Reasoning (CR) | Re: A survey of charitable giving in the state found that the

A survey of charitable giving in the state found that the average dollar amount contributed annually by residents of urban areas to programs for the homeless was $15 greater than the amount contributed by residents of rural areas. The survey’s creators, an urban-promotion group known as Live in the City, concluded that city dwellers are on average more generous than residents of rural areas.

EACH of the following, if true, casts doubt on the conclusion of the survey’s creators EXCEPT

A)An