In case of which one of the following biogeochemical cycles, the weathering of rocks is the main source of release of nutrient to enter the cycle?
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Answer: C. Phosphorus has no major gaseous phase. Its main reservoir is rocks, and weathering releases phosphates into soil and water. Carbon, nitrogen and sulphur cycles have large atmospheric reservoirs.
Watch for: Sulphur also comes from rocks, but phosphorus is the classic sedimentary cycle with rock weathering as the source.
Why the other options are wrong
- A. Wrong because carbon's main reservoir is the atmosphere and oceans.
- B. Wrong because nitrogen's main reservoir is the atmosphere.
- D. Wrong because sulphur has a significant atmospheric component too.
Source to check: NCERT Class 12 Biology (older edition), Chapter 14 Ecosystem, Nutrient Cycling
Answer from the official UPSC key. Written and fact-checked by AI against the official key. Spotted a mistake? Report it.