GMAT Critical Reasoning (CR) | Re: Many households have replaced at least one of their

Are we not assuming while discarding option B (and saying that it strengthens the argument) that the decrease in the amount of miles driven is due to the replacement of gasoline powered cars with electric ones? If the distance driven was going to be reduced regardless then the decrease in consumption of gasoline would've happened even without the replacement?

B seems like the tricky answer.

D says that electric companies use gasoline to produce "at least some" electricity but that does
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