The Atmospheric Oxygen at 1.9 billion years ago, was percent that of the modern level. A- 10% B- 15% C- 70% D- 50%

The continental Redbeds of soil in South AFRICA was aged by 1.9 billion years indicate that the atmospheric Oxygen at that time was that of the modern level A- 15 perecent B- 30 percent C- 70 percent D- 25 percent

Chose the correct statement(s)(a) A very thin envelope of gases that surrounded the earth at the time of its formation.(b) About 600 billion years ago plants and animals were formed on the Earth.(c) The two probable sources of oxygen in the atmosphere are photodissociation of watermolecule and evapotranspiration.(d) The evidence of oxygen in the ocean is noted between 2.5 and 3.0 billion years ago.(a) and (b)(b) and (c)(c) and (d)(a) and (d)

When the Earth was first formed there was no oxygen in the atmosphere.Explain how the atmosphere changed so that today it is 21% oxygen and only 0.04% carbon dioxide.

Earth's earliest atmosphere largely consisted of A- Oxygen B- methane and ammonia C- carbon monoxide D- none of the above

Oxygen makes up the majority percentage of both the human body and the Earth's crust. Oxygen also makes up a large percentage of which of the following?