The unit of productivity is $.........$

Secondary productivity is the rate of formation of new organic matter by:

$A$ is required for higher primary productivity. $B$ have the lowest primary productivity as the soil is deficient in moisture.
Choose the correct option for $A$ and $B$.

Net primary productivity $(NPP)$ in an ecosystem is:

For net primary productivity,the energy captured is:

Why are oceans the least productive ecosystems?