Which of the following is TRUE about acute pain?

As recently as the 1970s, little research existed about a subject that interests most people at some time. The subject is pain.
    Over the years, however, medical studies have led to new hope for patients who are hurting.
    And, an international movement known as Hospice has helped bring attention to difficult-to-treat pain for the dying.
    Doctors speak of three kinds of pain: acute, chronic and breakthrough. Acute and chronic pain can be mild or severe.(21)Acute pain happens fast and usually lasts a short time. It generally reacts to treatment.
    But chronic pain can last a long time. Chronic pain may go away, but it often comes back. It can be hard to treat.(22)Breakthrough pain is a pain that strikes suddenly. It may end just as suddenly. An activity can cause breakthrough pain.
    It also may happen as the effects of a person’s last medicine are ending.