The correct option is D Productivity
Interaction of biotic and abiotic components result in a physical structure that is characteristic for each type of ecosystem. Identification and enumeration of plant and animal species of an ecosystem gives its species composition. Vertical distribution of different species occupying different levels is called stratification. These are all structural aspects of an ecosystem. On the other hand, productivity is the rate of biomass accumulation at a specific period of time by the ecosystem. It is a functional aspect. It entirely depends on the energy flow and also on the above mentioned structural components of the ecosystem.