B. Fish kills, because of the lowered dissolved oxygen in the water
Explanation:
Eutrophication refers to the algal bloom as caused by increased levels of nutrients in water bodies. The algal population uses the dissolved oxygen and makes it unavailable or scarce for animals such as fishes present in the water bodies. The scarcity of oxygen leads to the death of fishes in a eutrophic water body.
The substrate and the active site both need to fit together perfectly in order for the enzyme to work properly. If their shape is changed, typically through heat or a change in pH, the enzyme will not work.
