Frodo, being a hobbit from the Shire, would likely be curious and intrigued if he saw a human for the first time. He would probably approach the human cautiously, wanting to learn more about this new and strange creature. Frodo may be slightly nervous or unsure, but his natural curiosity and friendliness would ultimately lead him to interact with the human and try to establish a friendly connection. Overall, Frodo would react with a mixture of wonder, curiosity, and a desire to learn more about this unfamiliar being.