One of the following atoms often limit the primary productivity of an ecosystem

With regard to ecological food chain, man is a

Which of the following is source of energy to an ecosystem

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

Standing state of the ecosystem is

$A$ : Detritus food chain begins with detritus.

$R$ : Detrivores like fungi and bacteria are major decomposers in such food chains.