Which one of these is not known?

Iron is rendered passive by treatment with

Given below are two statements for catalytic properties of transition metals. Statement $I$: First row transition metals which act as catalyst utilise their $3d$ electrons only for formation of bonds between reactant molecules and atoms on the surface of catalyst. Statement $II$: There is increase in the concentration of reactants on the surface of catalyst which strengthens the bonds in reacting molecules. In the light of the above statements, choose the correct answer from the options given below:

Which element can have oxidation state from $4$ to $6$?

Assertion $(A):$ $VF_5$ is stable while $VCl_5$ is not.
Reason $(R):$ Fluorine stabilizes the higher oxidation state due to its higher bond enthalpy.
The correct option among the following is

Which of the following statements is not correct?