UPSC CSE Prelims
Question 86
With reference to the planet Earth, consider the following statements :
- Rain forests produce more oxygen than that produced by oceans.
- Marine phytoplankton and photosynthetic bacteria produce about 50% of world's oxygen.
- Well-oxygenated surface water contains several folds higher oxygen than that in atmospheric air.
Which of the statements given above is/are correct?
View correct answer and explanation
Correct answer: B
Correct Option: B (II only)
Explanation: About half of global oxygen production comes from oceanic phytoplankton and photosynthetic microorganisms. Rainforests do not outproduce the oceans, and oxygen dissolved in surface water is far less concentrated than oxygen in air.
Statement / Pair / Item-wise Analysis:
I: False-oceans account for roughly half of global photosynthetic oxygen output.
II: True-marine phytoplankton and cyanobacteria produce around 50%.
III: False-air has far more oxygen per unit volume than dissolved oxygen in water.
Option-wise Analysis:
A. Incorrect-includes I despite the item-wise findings.
B. Correct-this matches the facts and the item-wise assessment above.
C. Incorrect-includes I, III despite the item-wise findings; omits II which the answer requires.
D. Incorrect-omits II which the answer requires.