There are a couple of theories on how it works.

Breaking a sweat may relieve stress, says Dr. Mauskop. Headaches are often triggered by stress, and if yoremove the trigger, yorelease the pain.

The feel-good chemicals produced when yoexercise actually block your pain sensors, acting as a natural painkiller.

Since headaches can be caused by many different factors like genetics (遗传 ),lack of sleep, or certain foods, cardio won't be the solution for everyone, Dr. Mauskop says. But one German study found that it helped 65 percent of patients, which makes it as effective as the best medicines on the market.

Dr. Mauskop recommends his patients do a half-hour reasonable intensity (强度 )cardio, like jogging, biking, or swimming three times a week. These workouts are meant to be slow and steady, as opposed to high-intensity intervals that alternate between all-out runs and rest.

Pushing yourself too much or increasing the intensity too quickly can trigger headaches in some people, so make sure your heart rate doesn't jump above 150 BPM. If yodon't have a heart rate monitor, then breathe only through your nose. Yo'Il know you're going too hard if yocan't keep up that breathing pattern.

Your migraines could start disappearing in a couple of weeks, Dr. Mauskop says.

29. According to the passage, the author may agree that

A. jogging, swimming and fishing are cardio workouts

B. neither cardio workouts nor topamirate has side effects

C. migraine patients may be cured by regular cardio workouts

D. cardio workouts will be the solution for everyone with migraines

30. The underlined word "triggered" in Paragraph 7 can be replaced by _

A. cured B. released C. caused D. monitored

31. The feel-good chemicals produced can help with regular headaches because

A. it eases the stress B. it breaks a sweat

C. it prevents migraines D. it blocks your pain sensors

32. What would be the best title?

A. A cure for headache. B. Side effects of migraine.

C. The causes of headache. D. Advantages of cardio workouts.

D

Try rubbing (摩擦 ) the tip of your finger backwards and forwards very quickly on your coat or a blanket. It should become hot. In cold weather we sometimes rub our hands together to make them warm. The rubbing of two together which causes heat is called "friction"(摩擦 力). In the same way, people who lived in caves rubbed a piece of wood shaped like a pencil on another piece of wood with dried leaves or grass packed nearby. The heat set the leaves or grass alight. This was a difficult way of making fire. Better ways were found by using flint(火石),but it was not until 1827 that the first matches were made in England.

Chemists made up a mixture and put it on an end of a stick or match. The mixture contained a small amount of phosphorous (磷),a chemical that bursts into flame when heated slightly. The other chemicals then caught fire and burned less fiercely until the wood was alight. By rubbing the end of the match, on sandpaper, the friction easily set the phosphorous alight. These first matches could also be struck on other rough surfaces, including the leather sole(底)of a shoe.

At the time, everyone thought this was a wonderful invention. Unfortunately accidents happened. A whole box of matches would suddenly catch fire if it was heated. Imagine this happening to someone warming themselves by a fire with a box of matches in his or her pocket! Even loose matches in a handbag or pocket could rub together and catch fire.

What was needed was a match that would only light if struck on a special surface. In 1852,the safety match was invented in Sweden. No phosphorous was used in the match head-it was put on the outside of the matchbox instead. This made it impossible for the match to light unless it was rubbed along the box on the special surface which contained sandpaper mixed with a little phosphorous.

33. Why did people use dried leaves or grass to pack another piece of wood?

A. The leaves or grass is easy to be alight.

B. The leaves or grass covered the wood well.

C. The leaves or grass help the air cause heat.

D. The leaves or grass acted as the role of match.

34. What did the chemists make the match of in 1827?

A. Leather sole, sandpaper and leaves. B. Wood, leather sole and sandpaper.

C. Phosphorous, wood and sandpaper. D. Phosphorous , sandpaper and flint.

35. If we used the safety match, we could see

A. loose matches could catch fire fiercely

B. phosphorous wasn't needed inside matchboxes

C. there were matches and sandpaper in matchboxes

D. the special surface containing sandpaper and phosphorous