Crowding on Mooreville's subway frequently leads to delays, because it is difficult for passengers to exit from the trains. Subway ridership is projected to increase by 20 percent over the next 10 years. The Mooreville Transit Authority plans to increase the number of daily train trips by only 5 percent over the same period. Officials predict that this increase is sufficient to ensure that the incidence of delays due to crowding does not increase.

Which of the following, if true, provides the strongest grounds for officials' prediction?
A. By changing maintenance schedules, the Transit Authority can achieve the 5 percent increase in train trips without purchasing any new subway cars.
B. The Transit Authority also plans a 5 percent increase in the number of bus trips on routes that connect to subways.
C. For most commuters who use the subway system, there is no practical alternative public transportation available.
D. Most of the projected increase in ridership is expected to occur in off-peak hours when trains are no sparsely used.
E. The 5 percent increase in the number of train trips can be achieved without an equal increase in Transit Authority operational costs.
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Premise: Crowding on Mooreville's subway(MS) => difficult to exit from the trains=> delay in travel
Ridership will increase by 20% in 10 years.
Conclusion: Increase of trains by 5 % in 10 years is sufficient to avoid crowding.

Need to find something that strengthens:
A. Not sure if it will reduce the crowding and also it weakens the conclusion.
B. It is just repeats the conclusion and cannot strengthen.
C. As there is no other alternative for travel, only train route need to make efficient. So, it strengthens the conclusion. Answer.
D. I am not sure if this supports the official's prediction to increase the trains by 5%.
E. This somewhat supports, but costs are not considered anywhere.

My Answer is C. but OG has other answer. Can anyone elaborate why OA is D?