How many $ATP$ molecule$(s)$ is/are directly formed during one turn of Krebs cycle?

Assertion: In Krebs cycle,there is a one step where substrate level phosphorylation occurs.
Reason: During the formation of succinyl $\text{CoA}$ to succinic acid,a molecule of $\text{GTP}$ is synthesized.

In Krebs' cycle,$GTP$ is formed in

Identify $A$ and $B$ in the given reaction:
$\text{Pyruvic acid} + \text{CoA} + \text{NAD}^+ \xrightarrow{\text{Mg}^{2+}} A + B + \text{NADH} + \text{H}^+$

Reduced coenzyme $FADH_2$ is formed between which of the following intermediates in the Krebs cycle?

During the citric acid cycle,various organic acids undergo decarboxylation. Which of the following organic acids of the cycle have $4C$,$5C$,and $6C$ respectively?