All of the answers are acceptable, but when a person gives you a compliment (like calling you beautiful) you should always add a "thanks" or "thank you" at the end. This would be the best response - "That is very kind of you to say so. Thanks" The other two responses will work. They are not incorrect, but they are a phrases not commonly used when receiving a compliment. You could just respond with "Thanks" if you wanted to.

just say thanks ..........that's all