【单选题】During November 2012, gasoline prices were falling, which made travel by car less expensive, but air fares remained as high as ever. If income is unchanged and air travel is a normal good, _________.
A.
the substitution effect is an increase in car travel and the income effect is a decrease in car travel
B.
both the substitution and income effects decrease car travel
C.
the substitution effect is an increase in car travel and there is no income effect on car travel
D.
both the substitution and income effects increase car travel