Magnitude of primary productivity is affected by

The percentage of light energy utilized for photosynthesis by higher plants is

Which must be preserved in an ecosystem, if the system is to be maintained

Consider the following four statements $(A-D)$ and select the correct option stating which ones are true $(T)$ and
which ones are false $(F)$.
Statements :
$(A)$ Vertical distribution of different species occupying different levels in a community is called stratification.
$(B)$ Net primary productivity minus respiration losses is the gross primary productivity.
$(C)$ Rate of biomass production is called decomposition
$(D)$ Annual net primary productivity of oceans is $55$ billion tons

In a food chain herbivores are