PT 61 S4 Q12

After the rush-hour speed limit on the British M25motorway was lowered ... ...

Which one of the following, if true, most helps to explain the decrease in travel times described above?
(A) After the decrease in the rush-hour speed limit, the average speed on the M25 was significantly lower during rush hours than at other times of the day.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Complete Section: LR-B, Oct. '10 LSAT (PT 61 Sec. 4)