What about trains? Nothing is mentioned about trains in the options and only barges

Also - for evaluate questions, do the answer choices add new information?

Trancorp currently transports all its goods to Burland Island by truck. The only bridge over the channel separating Burland from the mainland is congested, and trucks typically spend hours in traffic. Trains can reach the channel more quickly than trucks, and freight cars can be transported to Burland by barges that typically cross the channel in an hour. Therefore, to reduce shipping time, Trancorp plans to switch to trains and barges to transport goods to Burland.

Which of the following would be most important to know in determining whether Trancorp’s plan, if implemented, is likely to achieve its goal?
Question type: evaluate a plan
T (Trancorp) uses trucks to transport, which takes time. T comes with an another idea and says that we can use trains and barges to transport and we can reduce shipping time.
Missing information: There is a massive assumption that is hidden in the argument. The author takes it for granted that the suggested plan will work. I mean, think about it, how do we know that the suggested plan is even capable enough to succeed.

(A) Whether transportation by train and barge would be substantially less expensive than transportation by truck
Eliminate since we are more concerned with the saving the shipping time rather than the cost.

(B) Whether there are boats that can make the trip between the mainland and Burland faster than barges can
So what if the boat can make the trip. Do we know if the boats can be used in shipping? No, eliminate.

(C) Whether loading the freight cars onto barges is very time consuming
Spot on! That’s what we would like to know if we use barges to ship the cars, is that going to be time consuming since our main aim is to save time.

(D) Whether the average number of vehicles traveling over the bridge into Burland has been relatively constant in recent years
Out of focus. Eliminate.

(E) Whether most trucks transporting goods into Burland return to the mainland empty
Why on earth would we be interested in knowing if the trucks come empty or fully loaded? Eliminate.

I echo the same. C has solid reasoning but is only limited to barges,with no mention to trains, 'C' is making the option INCOMPLETE. Therefore I chose 'A'
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i understood the reasoning behind option c but it only mentions about barges and not about trains and the argument states that the plan is to switch to trains and barges not barges alone and this answer only tells about barges. if anyone can explain this would be helpful.