A client with coronary artery disease reports intermittent chest pain that occurs with exertion. The physician prescribes sublingual nitroglycerin. When teaching the client about nitroglycerin administration, the nurse should include which instruction ？（）
A．"Be careful after taking nitroglycerin because it may cause dizziness. "
B．"Make sure you replace your nitroglycerin tablets every 6 months to ensure potency. "
C．"A burning sensation after taking nitroglycerin indicates medication potency. "
D．"When you experience chest pain, take one tablet every 30 minutes until the pain is relieved. "