A) Carbon
B) Oxygen
C) Hydrogen
D) Nitrogen
Correct Answer: B
Solution :
The atmosphere of primitive earth was unlike our present atmosphere in following respects: 1. Abundance of hydrogen: The interstellar dust from which earth originated was especially rich in hydrogen. It readily combined with nitrogen forming ammonia, with oxygen forming water and with carbon forming methane. Thus early atmosphere of primitive earth was strongly reducing; it contained hydrogen, methane, ammonia and water vapours. 2. Absence of free oxygen: The early atmosphere was without free oxygen (none-oxygenic). It was bound in water, carbon monoxide and carbon dioxide and in metallic oxides on the surface rocks and particles. Because of the absence of free oxygen any complex organic compound that arose during early time were not subjected to degradation. 3. Absence of ozone layer : There was no layer of ozone to absorb utiraviolet rays coming on to earth from the sun.
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