The maximum evolution of oxygen is by which of the following producers of organic matter?

$A$: Decomposers are excluded from the food chains.
$R$: They act on all trophic levels of a food chain.

The energy obtained from fossil fuels is essentially a product of which of the following?

Match the following columns:

Column-$I$	Column-$II$
$(a)$ Earthworm	$(i)$ Pioneer species
$(b)$ Succession	$(ii)$ Detritivores
$(c)$ Ecosystem service	$(iii)$ Birth rate
$(d)$ Population growth	$(iv)$ Pollination

Observe the given chart and identify what it represents.

How many of the following organisms are decomposers in a pond ecosystem?
Some algae,fungi,bacteria,floating plants,submerged plants,flagellates.