An Insurance Underwriter Wonders Whether Sports Cars "Cause" People to Drive

An insurance underwriter wonders whether sports cars "cause" people to drive too fast or whether those with a propensity for speeding are drawn to sports cars. She secures some research funds and recruits 100 car buyers to her study. She randomly assigns 25 drivers to each of four groups: 1) sports car white, 2) sports car red, 3) sedan white, and 4) sedan red. The primary research questions are: 1) Do sports cars make people drive faster? and 2) Does color make a difference? The result shows that people driving red cars drive faster than those driving white cars. There is no statistically significant difference by type. This conclusion is:

A) wrong, because the stated purpose was to study type, not color.
B) valid, because this was a randomized study and drivers were randomized on color and type.
C) wrong, because you cannot study two different things, like type and color, at once.
D) valid, because sports cars obviously make people drive fast.