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The atmosphere and hydrosphere have kept about the same chemical balance for the last:
AOne million years
BTen thousand years
COne hundred years
DOne billion years
Answer & Solution
Correct answer: D. One billion years
1. Cyclic passage through organisms keeps the balance.
2. It has held for a billion years.
3. Solar insolation energises the cycles.
_Source: NCERT Class 11 Fundamentals of Physical Geography, Chapter 15, Life on the Earth._
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