What if I do not know the answer to a prospect's question?

Say this, exactly: "Great question. Let me verify that so I can give you accurate information." Then actually go find out and follow up. Here is why this works better than winging it. A wrong guess, discovered later, torches every other thing you told them. But "let me check" signals honesty, and the follow-up call it creates is another touch point you would not have had. Nobody expects you to know everything. They just need to trust everything you say. Never guess. Ever.