The correct option is C Saturn
Venus and Mars are terrestrial planets, meaning "Earth-like" planets. So, they have rocky crusts, and are primarily made of heavy metals like iron and nickel, etc. Therefore, they have a solid surface to land on, like our earth.
On the other hand, the planets Jupiter and Saturn, are called gas giants, because they are essentially giant spheres of hot hydrogen and helium gases. So, they don't have a true solid surface to land on.