Which one of the following types of organisms occupy more than one trophic level in a pond ecosystem?

Which of the following statements are correct?
$(a)$ Net primary productivity is available biomass for consumption to heterotrophs.
$(b)$ Secondary productivity is defined as the rate of formation of new organic matter by heterotrophs.
$(c)$ The annual net primary productivity of the ocean is greater than that of land.
$(d)$ Warm and moist environment favours decomposition.

Choose the correct sentence.

Which of the following ecosystems is both man-made and aquatic?

In a food chain, which of the following is produced in the largest amount?

Identify the basic components of an ecosystem.