Multiple choice

Which of the following gases was absent at the time of origin of life?

  1. Oxygen

  2. Methane

  3. Hydrogen

  4. Ammonia

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Early Earth had a reducing atmosphere composed mainly of methane, ammonia, hydrogen, and water vapor. Free oxygen was essentially absent because it reacts rapidly with reducing compounds and was only produced later by photosynthetic organisms.