In submerged hydrophytes,the entry of $CO_2$ is through:

$A-$ In stroma,enzymatic reactions synthesize sugar which in turn forms starch.
$R-$ The membrane system of chloroplast is responsible for trapping the light energy and also for the synthesis of $ATP$ and $NADPH$.

Which one of the following categories of organisms does not evolve oxygen during photosynthesis?

Statement $P$: During the dark reaction of photosynthesis,ketotriose is synthesized.
Statement $Q$: The sugar present in the structure of $ATP$ is an example of a ketopentose sugar.

Approximately $9/10$ $(85-90\%)$ of the total photosynthesis on Earth is carried out by:

According to one estimate,how many $kg$ of carbon is fixed in the biosphere through photosynthesis annually?