Enzymes,which catalyse the joining of $C-O, C-S, C-N, P-O$ etc. bonds,are included in which of the following classes?

Assertion $(A)$: All enzymes are made of proteins.
Reason $(R)$: All proteins act as enzymes.

When an enzyme-induced product inhibits enzymatic activity,the inhibition is called:

In plants,enzymes are present:

Study the following statements:
$(a)$ The substrate binds to the active site of the enzyme.
$(b)$ Enzymes isolated from thermophilic organisms get denatured at $50^{\circ}C$.
$(c)$ The active site of the enzyme breaks the chemical bonds of the product.
$(d)$ Prosthetic groups are tightly bound to the apoenzyme.
Select the option which includes all correct statements:

The number of active sites in an allosteric enzyme is: