听一段材料，回答下面几个小题。
Which can best describe a tension headache?
A. It occurs repeatedly.
B. It lasts over a month.
C. It causes severe pain.
Which is a symptom of tension headaches?
A. Loss of consciousness.
B. Increased blood pressure.
C. A pain at the back of the head.
What is the cause of rebound headaches?
A. Stressful events.
B. Tension in the muscles.
C. Too much use of pain medicine.(http://www.171english.cn)
Why is a headache diary helpful for the treatment?
A. It helps one find the cause of his headaches.
B. It reminds one to take medicine on time.
C. It helps remove constant pain.