Planet a is an inner planet with no moon and hardly any atmosphere. Planet b is an inner planet with no moon but with dense atmosphere

In our solar system there are two inner planets that do not have a moon; Mercury and Venus.

Planet A is assumed to be Mercury because it has a very thin virtually nonexistent atmosphere and no moon.

Planet B is assumed to be Venus because the planet has a dense toxic atmosphere. However, like Mercury, Venus has no moon of its own.