Final answer:
Catherine tells Nick that Tom can't divorce Daisy because she is Catholic and the Catholic Church does not believe in divorce.
Step-by-step explanation:
In the novel The Great Gatsby, Catherine informs Nick that the reason Tom cannot divorce Daisy is that Daisy is Catholic, and Catholics do not believe in divorce. This cultural context is significant within the novel as it affects the characters' decisions and relationships. The implications of Daisy's Catholicism serve to trap her in a loveless marriage, highlighting the themes of unhappiness and the inescapability of one's social situation in the story.