Select the correct statement about productivity from the following.

Options

A. Gross primary productivity is the available biomass for the consumption to heterotrophs.
B. Secondary productivity depends on the photosynthetic capacity of the plant species inhabiting a particular area.
C. Productivity is expressed in terms of `kg^(-2)yr^(-1)` or `(kcal m^(-2))yr^(-1)` to compare the productivity of different ecosystems.
D. Of an approximate NPP of 170 billion tonnes, the productivity of the oceans are only 55 billion tons despite accupying 70% of the earth.

Answer

D