Since there is only one reacting species in a unimolecular reaction. Thus it is involved in the rate-determining step.

For a unimolecular reaction, molecularity is one as only one reacting species are involved in the reaction.

Thus option(i) is correct.

Since the rate of the reaction depends upon the molar concentration of one reactant, the order of the reaction is also one.

Thus option (ii) is also correct

Option (iii) is false as the order of a reaction is 1, not 0.

A ……….. (unimolecular reaction)

Rate=k[A]

Order= 1

Molecularity= 1

Thus option (iv) is correct.