Answer:
The unsuitability of a match between him and Harriet.
Step-by-step explanation:
Emma is a novel written by Jane Austen.
Emma Woodhouse is the main character of the story. She is beautiful and intelligent, but also she is a little spoiled. Although she is kind to the poor, she has a strong sense of class status. She thinks that she knows everything, but due to the lack of experience, she makes a lot of mistakes.
All of these characteristics we can see in the situation with Harriet and Mr. Martin. Harriet is a friend of Emma who is poor and without a high status in society. Emma takes Harriet under her wing, and she tries to find a good husband for Harriet, based on her judgments. When Mr. Martin proposes to Harriet, Emma makes her refuse him as she thinks that Mr. Martin is not a good match for her and that Harriet can find a better husband. But that was only Emma's perspective. On the other hand, Harriet loves him, but she listens to her friend.
I hope it helped you :)