Why do you want to sell our product/service?

A successful salesperson usually believes in the product or service that they are selling. This helps them to come across as sincere when interacting with potential customers. Since as a fintech business development representative you'll be one of the people on the front lines who convinces prospects to try or buy their product, the interviewer wants assurance that you'll be able to effectively do this. Tell the interviewer with enthusiasm why you're interested in selling their product/service. You might also mention your affinity for finance and technology as well.