WAEC Biology 2014 Question 36

The table below shows the oxygen level, number of green plants and fish in rivers flowing through four towns.
Town A: oxygen level high, green plants few, fish many.
Town B: oxygen level low, green plants many, fish many.
Town C: oxygen level high, green plants few, fish few.
Town D: oxygen level low, green plants many, fish few.
Which of the towns is likely to be discharging untreated sewage in their river?

1. A.A.
2. B.B.
3. C.C.
4. D.D.