Answer:
I believe the answer is D. Rock
Step-by-step explanation:
The cores of the outer planets (Jupiter, Saturn, Uranus, and Neptune) are believed to be formed mainly of rock and metal, with smaller amounts of hydrogen, helium, and other gases. These planets are often referred to as gas giants, but their cores are thought to be solid and rocky. The outer layers of these planets consist of hydrogen and helium gases and are very thick and massive. Additionally, some of these planets have icy layers on top of their rocky cores.