Demand for Airline Travel Usually Increases During the Summer

Multiple Choice

Demand for airline travel usually increases during the summer. One explanation is that

A) VIA Rail offers price discounts during the summer.
B) consumer incomes are lower in the summer and airline travel is a normal good.
C) consumer incomes are higher in the summer and airline travel is an inferior good.
D) there are more customers during the summer.
E) hotel prices rise during the summer.