Oxygen on Earth mainly comes from photosynthesis, especially by phytoplankton (marine organisms), and oxygen levels differ between air and water.

❌ Statement I is incorrect:

• Oceans (phytoplankton) produce more oxygen than rainforests.

✅ Statement II is correct:

• Marine phytoplankton and photosynthetic bacteria produce about 50% of the world’s oxygen.

❌ Statement III is incorrect:

• Atmospheric air has much more oxygen than surface water; water does not contain several folds higher oxygen than air.

So, the correct answer is: B