Answer:
Hydrogen and helium
Step-by-step explanation:
The gas giants are the bigger planets that are located outside of the asteroid belt. These are Jupiter, Saturn, Uranus, and Neptune. They are primarily comprised of hydrogen and helium gas. These gases are very light and easily escapable. But they are present in these jovian giants and absent in the inner terrestrial planets. It is because the force of gravity in these planets is relatively high that enables the atmosphere to hold these gases in it.
The distance of these planets is also very far away from the sun and their atmosphere is comparatively cold.