What are the two gases that escaped earth's atmosphere during early formation?
a. helium and nitrogen
b. helium and oxygen
c. hydrogen and helium
d. hydrogen and nitrogen

Option (C)

Explanation: Hydrogen and Helium initially, both were present on the earth's atmosphere. But later they were reduced upto a huge extent. Due to the location of earth near to the sun, these gases must have evaporated from the earth's atmosphere. At present the amount of hydrogen and helium is very less.

Thus, the correct answer is option (C).

try answer.com that works for me

it is the most commonly accepted one