Respuesta :
Answer: D. hydrogen and helium
Explanation:
The Earth formed approximately 4.5 billion years ago. The oxygen was absent in the primitive atmosphere. Earth's primitive atmosphere could probably exhibited hydrogen and helium. These were the main gases which were responsible for making the earth atmosphere hot on early earth. These two gases where lighter in mass as compared to other gases. These used to escape to the space from the early planet earth. Today earth just consists of only 1 percent of the helium and hydrogen.
