I was thinking that everyone is different from the rest in its own ways, and they all are, but I would have to say the earth. The earth is the only one of the planets that has (from what we know) substantial amounts of liquid water, a perfect climate in the so-called "Goldilocks Zone" (i.e. not too hot and not too cold), and (from what we know) the only one that sustains life. Grammatically, Jupiter is the one that doesnt belong, because it has 3 vowels and the others only have two, and it is the one that is a gas giant. Mercury has no atmosphere. Venus has a runaway greenhouse effect, with surface temperatures far above the boiling point of water.