In "When Is a Planet Not a Planet?" why does the author say that the outer planets are made of gas when the inner planets are made of rock and dirt? A. All the gas from the inner planets floated to the outer planets. B. The outer planets did not experience the force of the sun that blasted the gas from the inner planets. C. The outer planets remained gas because they were bigger. D. The outer planets were generally hotter, so they remained made out of gas.