What gas did not appear in any measurable amount until about 2.0 BY BP?

The correct answer is Oxygen.

Explanation:

2.0 BYBP means 2 billion year before present.

The theory of evolution holds that the the synthesis into primitive life forms of the basic chemical components of life such as carbon, nitrogen, hydrogen and oxygen occurred in an atmosphere without any oxygen.

The presence of oxygen in our plant today is explained by two processes.

They are:

The process of Photosynthesis which is the chief contributor of oxygen to the earths atmosphere is said to have spanned billions of years.

Cheers!

answer: that would be cheating

explanation:

answer; i believe the answer is (polygenic inheritance;