A. people have been spreading negative rumors about Gatsby's past.
Explanation:
When the narrator shows what the girl said about Gatsby, we can see that he is a controversial figure within the society that is inserted. Nobody knows much about him and with this mysterious past and the economic rise so fast that he presents, people start creating rumors and stories about him, many of these stories are negative, like the one that the girl heard.
With that, we can say that from the girl's speech, we can infer that people created negative rumors about Gatsby.
