The trains in the stories symbolized the journey the characters underwent to get what they want.
The trains are also the witnesses to the death of the characters. In the story "Paul's case" Paul committed suicide by jumping in front of a train. In the story "A Journey" the husband died in his sleep inside the train while the wife accidentally died when the train reached its destination.
It also sends a message of whatever journey one enjoys in life, he/she will always end up dead or death is an inevitable destination.
We are reading this in class, and I believe the answer would be b, because he is really amazed at everything that Gatsby does to set up his hose for a party that lasts a night...... I really hope that the answer is right the book is kinda boring in my eyes, but yeah... sorry if I am wrong.....
B) To entertain the reader