The exchange pool in the carbon cycle is:

How many sentences are correct?
$(1)$ The trophic levels in $GFC$ are unlimited.
$(2)$ Organisms at each trophic level depend on those at the higher trophic level for their energy demands.
$(3)$ Plants capture only $2-10$ percent of $PAR$.
$(4)$ All organisms are dependent for their food on producers, either directly or indirectly.

Pisaster is a . . . . . . .

Identify the mismatched pair from the given options.

Which of the following ecosystems is both man-made and aquatic?

Identify the correct type of food chain.
Dead animal $\rightarrow$ Blow fly maggots $\rightarrow$ Common frog $\rightarrow$ Snake