In a food chain of a grassland ecosystem,the top consumers are

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.

Given below are two statements:
Statement $I$: In an ecosystem,there is a unidirectional flow of energy from the sun through producers to consumers.
Statement $II$: Ecosystems are exempted from the $2^{nd}$ law of thermodynamics.
In the light of the above statements,choose the most appropriate answer from the options given below:

Carbon constitutes . . . . . . of dry weight of organisms and . . . . . . percentage is dissolved in oceans out of total global carbon.

In a pond ecosystem,which organisms can occupy more than one trophic level?

Consider the following statements concerning food chains.
$A.$ Removal of $80\%$ tigers from an area resulted in greatly increased growth of vegetation.
$B.$ Removal of most of the carnivores resulted in an increased population of deers.
$C.$ The length of food chains is generally limited to $3-4$ trophic levels due to energy loss.
$D.$ The length of food chains may vary from $2$ to $8$ trophic levels.
Which two of the above statements are correct?