Scientific evidences suggest that oxygen gas appeared on earth about ____ years ago.
A) 38,000,000,000
B) 25,000,000,000
C) 2,300,000,000
D) 380,000,000
E) 4,500,000

Question

Quizplus · Accepted Answer

Scientific evidences suggest that oxygen gas appeared on earth about 2.3 billion years ago. This is based on the presence of banded iron formations, which were formed through the reaction of oxygen with iron in seawater. These formations are only found in rocks that are younger than 2.3 billion years old.

Scientific Evidences Suggest That Oxygen Gas Appeared on Earth About