In aerobic respiration,which of the following statements is correct regarding the respiratory substrate?

Ganong's respiroscope is used to demonstrate........

Given below are two statements:
Statement-$I$: Acetyl $CoA$ formation takes place by oxidative decarboxylation of pyruvic acid.
Statement-$II$: $\beta$-oxidation of fatty acid produces acetyl $CoA$.
In the light of above statements,choose the most appropriate answer from the options given below.

$A$ student has taken a twig from a plant. She/he observes a droplet of fluid exuding from the cut surface of the twig. What is this fluid?

Which of the following is not correct with reference to fermentation and aerobic respiration?

What is the significance of the Krebs cycle?