In the following three sentences, two are facts and one is an opinion . Earth is a planet where animals and plants can live. Earth is the third planet from the sun. Earth is the most beautiful planet. You got out of correct.
Earth is the most beautiful planet is an opinion.
Some people believe that Saturn, with its beautiful rings, is the most beautiful planet. It is true that animals and plants live on Earth, the third planet from the sun. Each of the other sentences states a fact, or something that is a certainty. A fact does not change from person to person, or from place to place.