Which of the Following Is the Best Explanation for Why

Which of the following is the best explanation for why the price of gasoline increases during the summer months?

A) There is less competition among oil refineries in the summer.
B) Sellers have to earn profits during the summer to cover losses in the winter.
C) There is increased driving by families going on vacation.
D) The number of gas stations open 24 hours a day rises in the summer months and so the price must rise to cover the higher costs.
E) Oil producers have higher costs of production in the summer.