$DNA$ is present in

Select the alternative giving correct identification and function of the organelle '$A$' in the diagram.

Which statement is correct regarding mitochondria?

Which membrane of the mitochondrion has a greater surface area?

In which part of mitochondria does $ATP$ synthesis occur?

$A$: Janus green $B$ is a vital stain for locating mitochondria.
$R$: Janus green is oxidised by cytochrome oxidase present in mitochondria.