A. It caused the planets to heat up, boiling off any water on their surfaces and leaving them barren.
The inner planets, also known as the terrestrial planets, are Mercury, Venus, Earth, and Mars. They are smaller and denser than the outer planets, and they are primarily composed of rock and metal. When they formed, their close proximity to the sun caused the planets to heat up, boiling off any water on their surfaces and leaving them barren. This is why the inner planets are mostly dry and rocky, with little to no surface water or ice. The heat also caused their surfaces to melt, resulting in volcanic activity and the formation of solid rocky surfaces.