A、A section of the railway has got damaged. B、It is too foggy for the driver to see clearly. C、Part of the line is covered with

M: Um, excuse me. Did I just hear that the Preston to Lancaster service has been cancelled again?
W: Well, sir, it won’t be running today.
M: Would that be because of the snow in the Tring Gap? You’ ve had three days to get that line clear.
W: Well, actually, sir, the snow melted earlier today and that part of the line’ s a foot under water now. And if we did run any trains along there, we’ d be having an accident and I’ m sure that you wouldn’ t…
Question: What is the cause of the train’ s delay?