Which Statement Made by the EMT Indicates a Safe Understanding

Which statement made by the EMT indicates a safe understanding of the administration of nitroglycerin in the prehospital setting?

A) "I always check for an allergy to sulfa, since most people with an allergy to sulfa also have an allergy to nitroglycerin."
B) "Since nitroglycerin constricts the blood vessels, you must always check the blood pressure before and after giving it."
C) "A total of three nitroglycerin tablets may be administered in the prehospital setting, and this includes what the patient takes prior to EMS arrival."
D) "If the patient with chest pain also has a headache, the EMT should contact medical command prior to administering nitroglycerin."