The detectable end product of photosynthesis is

$A-$ 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 $NADPH$.

Analogy type questions:
$(1)$ $C_4$ plants : Show $CO_2$ saturation at $360 \,\mu l L^{-1}$ :: $C_3$ plants : Show $CO_2$ saturation at concentrations above ............
$(2)$ Green plants : $H_2O$ as hydrogen donor :: Green sulfur bacteria : ............

Select the incorrect statement.

The most vital process for the existence of life on Earth is

Plants in which the first product of $CO_{2}$ fixation is $C_{3}$ acid,i.e.,the ...$A$... pathway,and those in which the first product was $C_{4}$ acid $(OAA)$,i.e.,the ...$B$... pathway. Complete the given statement by filling appropriate options in the given blanks.