Which of the following habitats is most unsuitable for primary productivity?

Answer: Option C

Cave habitats are most unsuitable for primary productivity.
It is damp, cool, and lacks light but temperature and humidity vary widely. This is the area that has the greatest abundance and diversity of life. Cave habitats can be divided into three zones.
Its relatively small amount of food, which all comes from outside of the caves and is brought in by sinking rivers and percolating water, by different animals (e.g. bats), as well as by falling in the caves.