According to M$8$Mrs Proposition Two, what impact does financial leverage have on a firm's cost of equity and its weighted average cost of capital?

$($Select the best choice below$)$

A$.$ As the amount of debt in the capital structure increases, the firm's cost of equity increases and $30$ does is WACC.

B$.$ As the amount of debt in the capital structure increases, the flmis cost of equity decreases while is WACC stays the same.

C$.$ As the amount of debt in the capial structure increases, the firm's cest of equity increases but its WACC decreases.

D$.$ As the amount of debt in the captal structure increases, the firm's cost of equity increases while its WMCC stays the same.