How much carbon is dissolved in the oceans (in $; \%$)?

Succession in a $6 \ m$ deep pond exhibits a sequence of

Biological equilibrium is found among the

Mr. $X$ is eating curd/yoghurt. For this food intake in a food chain,he should be considered as occupying:

If less light falls on the pond's surface,what is the most likely consequence for the fish population?

Consider the following statements about food chain:
$I.$ The transfer of energy from producers to top consumers through a series of organisms is called a food chain.
$II.$ $A$ food chain is always straight and proceeds in a progressive straight line.
$III.$ In a food chain,there is a unidirectional flow of energy from the sun to producers and subsequently to a series of different types of consumers.
Which of the statements given above are correct?