Car owners who inflate their tires properly can substantially boost their vehicles' fuel efficiency, since the increase in car-road friction can waste up to five percent of car fuel by underinflation.

(A) Car owners who inflate their tires properly can substantially boost their vehicles' fuel efficiency, since the increase in car-road friction can waste up to five percent of car fuel by underinflation.
(B) Because the underinflation of tires can waste up to five percent of a car's fuel by increasing car-road friction, car owners can substantially boost their vehicles' fuel efficiency by properly inflating the tires.
(C) Their vehicles' fuel efficiency is substantially boosted by car owners through the proper inflation of tires that, when underinflated, can waste up to five percent of car fuel by an increase in car-road friction.
(D) The proper inflation of tires by car owners, due to the fact that underinflation can waste up to five percent of a car's fuel by the increase of car-road friction, can substantially boost their fuel efficiency.
(E) Because up to five percent of a car's fuel are wasted through the increases in car-road friction when the tires are underinflated, car owners properly inflating tires can substantially boost their fuel efficiency.

Q/A-b