Of the gases listed, nitrogen, oxygen, water vapor, carbon dioxide, methane, nitrous oxide, and ozone are extremely important to the health of the Earth's biosphere. The table indicates that nitrogen and oxygen are the main components of the atmosphere by volume.
so the answer is D. Nitrogen and oxygen
hope this helps!
D. precision. At first glance you can mark out A and B because the answers does not relate to the question. If question had said "what do you call it when the measurement is close to the actual answer" then you would have picked C. So that leaves you D. precision.
<u>Answer:</u> The correct answer is Option d.
<u>Explanation:</u>
We are given:
Mass percentage of 
= 20 %
So, mole fraction of = 0.2
Mass percentage of 
= 30 %
So, mole fraction of = 0.3
Mass percentage of 
= 35 %
So, mole fraction of = 0.35
Mass percentage of 
= 15 %
So, mole fraction of = 0.15
We know that:
Molar mass of = 16 g/mol
Molar mass of = 28 g/mol
Molar mass of = 26 g/mol
Molar mass of = 48 g/mol
To calculate the average molecular mass of the mixture, we use the equation:
where,
= mole fractions of i-th species
= molar masses of i-th species
= number of observations
Putting values in above equation:
Hence, the correct answer is Option d.
The Great Oxidation Event (GOE), sometimes also called the Great Oxygenation Event, Oxygen Catastrophe, Oxygen Crisis, Oxygen Holocaust,[2] or Oxygen Revolution, was a time period when the Earth's atmosphere and the shallow ocean first experienced a rise in oxygen, approximately 2.4 billion years ago (2.4 Ga) to 2.1–2.0 Ga during the Paleoproterozoic era.[3] Geological, isotopic, and chemical evidence suggests that biologically produced molecular oxygen (dioxygen, O2) started to accumulate in Earth's atmosphere and changed Earth's atmosphere from a weakly reducing atmosphere to an oxidizing atmosphere,[4] causing many existing species on Earth to die out.[5] The cyanobacteria producing the oxygen caused the event which enabled the subsequent development of multicellular forms.
