In the atmosphere of the primitive earth there was no ________

A. Oxygen

B. Carbon dioxide

C. Nitrogen

D. Ammonia

Answer: Option A

Solution(By Examveda Team)

For decades, scientists believed that the atmosphere of early Earth was highly reduced, meaning that oxygen was greatly limited. By 2.7 billion years ago, a new kind of life had established itself: photosynthetic microbes called cyanobacteria, which were capable of using the Sun's energy to convert carbon dioxide and water into food with oxygen gas as a waste product.