一道语法题，求解

unimelb86

The number of people flying first class on domestic flights rose sharply in 1990, doubling the increase of the the previous year.

a. doubling the increase of
b. doubling that of the increase in
c. double as much as the increase of
d. twice as many as the increase in
e. twice as many as the increase of





OA: A  求解