The correct answer is B.
Gatsby's parties were always crowded. This seemed to indicate that Gatsby was a very popular and loved man, and that he had many friends.
However, after his death, only a small group of people besides attended his funeral. This small group included the narrator, Nick, some servants, the West Egg postman, the minister overseeing the service, Owl Eyes and Gatsby's father.
This is a very ironic turn of events in the ending story, showing that Gatsby's popularity was not real. People only cared about his parties, not about him.