Which one of the following statements related to the M&M Propositions is correct?

Question $5$ options:

i$)$

M&M Proposition II$,$ without taxes, implies that the cost of equity remains constant as a firm increases its debt$-$equity ratio.

ii$)$

M&M Proposition I, with taxes, implies that the ideal capital structure exists at a debt$-$equity ratio of $\mathrm{.}5.$

iii$)$

M&M Proposition I, without taxes, implies that the WACC of a firm remains constant even if the capital structure is changed.

iv$)$

M&M Proposition I, with taxes, implies that the capital structure of a tax$-$paying firm is irrelevant.