Maximum productivity is found in

Regarding the Gross Primary Productivity $(GPP)$ and Net Primary Productivity $(NPP)$ of an ecosystem,which of the following statements is correct?

Given below are two statements:
Statement $I$: The primary source of energy in an ecosystem is solar energy.
Statement $II$: The rate of production of organic matter during photosynthesis in an ecosystem is called net primary productivity $\text{(NPP)}$.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following ecosystems will be more productive in terms of primary productivity? Justify your answer: $A$ young forest,a natural old forest,a shallow polluted lake,an alpine meadow.

In the equation $GPP - R = NPP$ (where $GPP$ is Gross Primary Productivity and $NPP$ is Net Primary Productivity),$R$ represents:

Which of the following ecosystem types has the highest annual net primary productivity?