Answer:
Third Option: It was very hard for the morning sun to pierce
Step-by-step explanation:
The author means to say that the morning was so damp and misty that day (sunlight) succeeded with great difficulty in breaking the mist. Means, sunlight could not pass through the mist. In next line he further explains this fact that things even a few yards away could not be identified because of mist.
First option is incorrect as the sun could not make its way through mist, It was not possible to identify things even a few yards away from carriage windows.
Second option is incorrect because the author in the passage says "with great difficulty that the day succeeded in breaking". So, the day did break albeit with great difficulty.
Fourth option is incorrect because there is no mention of two men and depression by lack of sunlight in train.