Why is this the answer?

The answer is thanks because this riddle is a clever word puzzle about something everyone says almost every day: "thank you" or simply "thanks." The riddle is a trick because it makes you think of physical things you can actually borrow, like a book, a pencil, or money. You would borrow those items, and then you would return them to the owner when you are done. Think carefully about the word "borrowed." When you borrow something, you take it from a friend for a little while, and you promise to give it back later. You would never borrow a "thank you" from someone else. Gratitude is a feeling that comes from your own heart; you do not take it from another person first. It is always a new feeling that you create inside yourself. Now, let's look at the word "returned." When you say "thank you" to a person, it is a way of returning their kindness. Imagine your teacher helps you with a difficult math problem. They gave you help. What do you give them back? You return their good deed with a "thank you" and a smile. If a friend gives you a birthday present, you "return" their thoughtful action with your gratitude. A "thank you" is like a gift you give back immediately that says, "I noticed what you did, and it made me happy." It is one of the kindest things you can give because it shows respect and appreciation. You are not handing back a physical object; you are giving an expression of your good feelings. Since you never borrow gratitude to begin with, the only thing you are doing is returning the positive energy that someone gave to you. Saying "thanks" is a perfect way to show people that you noticed their generosity, and it often makes them want to be kind again. The two words, "borrowed" and "returned," sound like they are talking about an object, but they are actually talking about an important action you perform with words every day.