What were the main components of earth’s earliest atmosphere?

a. oxygen and nitrogen

b. oxygen and ammonia

c. hydrogen and nitrogen

d. hydrogen and helium

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.  

easy

explanation:

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.