Answer:
A) Some of the most financially successful households are the two-income houses, a high percentage of which have kids.
Explanation:
Sport cars are expensive, frequently costing over 100,000, if the income of the households composed by two persons is higher than on average than the income of the households composed by one single person, then, it is more likely that two-income households will buy more sport cars than one-income households.
Besides, as explained in the question, most of two-income households are married couples, many of them have kids, on average two, reason why a four door car simply makes sense to them.