Which of the Following Statements Concerning Severe Allergic Reactions Is

Which of the following statements concerning severe allergic reactions is true?

A) The quicker the onset of symptoms, the greater the likelihood of a severe allergic reaction.
B) A severe allergic reaction can be prevented by the use of an epinephrine auto-injector before exposure to the substance.
C) Allergies do not develop until a person is in his late teens to early 20s.
D) A severe allergic reaction occurs only when the patient has never been exposed to the substance before.