Where does the Krebs cycle take place?

In the $Krebs$ cycle,$FADH_2$ is produced during the conversion of which of the following?

The largest amount of phosphate bond energy is produced in the process of respiration during

Provide the schematic representation of an overall view of the Krebs cycle.

Match the enzyme involved in the Krebs cycle given in column-$I$ with the reactions they catalyse given in column-$II$. Choose the correct option.

Column $I$	Column $II$
$i.$ Isocitrate dehydrogenase	$a.$ Citrate $\rightarrow$ Cis-aconitate
$ii.$ Fumarase	$b.$ Succinate $\rightarrow$ Fumarate
$iii.$ Aconitase	$c.$ Fumarate $\rightarrow$ Malate
$iv.$ Succinate dehydrogenase	$d.$ Isocitrate $\rightarrow$ Oxalosuccinic acid

In which of the following steps of the Krebs cycle is $CO_2$ released?