With reference to the planet Earth, consider the following statements:
I. Rain forests produce more oxygen than that produced by oceans.
II. Marine phytoplankton and photosynthetic bacteria produce about 50% of world's oxygen.
III. Well-oxygenated surface water contains several folds higher oxygen than that in atmospheric air.
Which of the statements given above is/are correct?
A.I and II
B.II only✓ Correct
C.I and III
D.None of the above statements is correct
Explanation
Oceans, primarily through marine phytoplankton and cyanobacteria, produce approximately 50-80% of the Earth's atmospheric oxygen, which is more than rainforests. Therefore statement I is incorrect, and statement II is correct. Atmospheric air contains about 21% oxygen by volume, whereas dissolved oxygen in well-oxygenated surface water is only about 8-10 mg/L, which is far less than atmospheric concentration — so statement III is incorrect. Only statement II is correct.
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