The correct option is D All of the above
Primary productivity is the process by which organisms make their own food from inorganic sources. The majority of primary producers are terrestrial plants and microbial life, such as algae.
Primary productivity due to photosynthesis is commonly measured by quantifying oxygen production or CO2 assimilation.
The primary productivity of an ecosystem is the rate at which biomass or organic matter is produced per unit area per unit time by plants(primary producers). Primary productivity depends upon plant species of the area, their photosynthetic capacity, availability of nutrients, solar radiations, precipitation, soil type and a number of other environmental factors.
So, the primary productivity of plants in an ecosystem depends on a variety of environmental factors, availability of nutrients and photosynthetic capacity of plants.