The main idea is:
B.True joy is experienced after difficult battles are won.
Explanation:
The passage builds up to the final moment of joy after the trial and tribulation of the life of the immigrants who had moved from Italy to the Us in search of a new life.
Now they are seeing in front of them the new life they had been looking for so desperately and this makes them happy beyond anything they had been happy for in the time that took them to be there.
This is the happiness that comes with over coming certain odds and not otherwise.