Planet a is an inner planet with no moon and hardly any atmosphere. planet b is an inner planet with no moon but with a dense atmosphere. which pair of planets is being described?
mars and venus
mercury and earth
mercury and venus
mars and earth

If we represent the solar system on a scale that allows us to walk from the sun to pluto in a few minutes, then a) the planets are microscopic and the stars are millions of miles away. b) the planets are the size of basketballs and the nearest stars are a few miles away. c) the planets are marble size or smaller and the nearest stars are thousands of miles away.