When the Nurse Is Administering Topical Nitroglycerin Ointment, Which Technique

When the nurse is administering topical nitroglycerin ointment, which technique is correct?

A) Apply the ointment on the skin on the forearm.
B) Apply the ointment only in the case of a mild angina episode.
C) Remove the old ointment before new ointment is applied.
D) Massage the ointment gently into the skin, and then cover the area with plastic wrap.