Why Does MM Proposition I Not Hold in the Presence

Why does MM Proposition I not hold in the presence of corporate taxation?

A) Bondholders require higher rates of return when their interest payments are taxed.
B) Dividends are no longer relevant when taxes are introduced.
C) A levered firm will pay less tax than the same firm unlevered.
D) The cost of equity increases with leverage.
E) The pretax cost of debt increases when taxes are considered .