Critical Reasoning

In the two years following the unification of Germany in 1989, the number of cars owned by residents of East Germany and the total distance traveled by cars in East Germany both increased by about 40 percent. In those two years, however, the number of East German residents killed each year as car occupants in traffic accidents increased by about 300 percent.

Which of the following, if true, most helps to explain the disproportionate increase in traffic fatalities?

(A) The average number of passengers per car was higher in the years before unification than it was in the two years after.
(B) After unification, many people who had been living in East Germany relocated to West Germany.
(C) After unification, a smaller proportion of the cars being purchased by East German residents were used vehicles.
(D) Drivers who had driven little or not at all before 1989 accounted for much of the increase in the total distance traveled by cars.
(E) Over the same two-year period in East Germany, other road users, such as motorcyclists, bicyclists, and pedestrians, experienced only small increases in traffic fatalities

OA [spoiler]D
But why not A[/spoiler]