The productivity of an ecosystem is composed of which of the following?

Correct option is D

The productivity of an ecosystem is composed of Net primary productivity and gross primary productivity.
Gross primary productivity (GPP) is the total rate of photosynthesis or the amount of energy produced by the primary producers of an ecosystem.
Net primary productivity (NPP) is the rate at which energy is stored in the organic matter of the primary producers after accounting for the energy used in respiration (R).
In other words,
NPP = the amount of energy that is available for the consumers in the ecosystem.
GPP = total amount of energy that is available for transfer to the next trophic level in the ecosystem.