Rick Garcia is going to play outside with his friends. He is taking out his reliever inhaler   and taking two puffs  . Five minutes later, he's on the field with his friends, running after a soccer ball. Rick has asthma  , but he knows how to control it. Asthma is a lung disease. A person with asthma may cough or suffer from shortness of breath. Asthma can begin at any age. Childhood asthma, often beginning when a child is younger than 10 years old, is one of the most common childhood diseases. Doctors report that the number of young people with asthma is increasing. It is the number one cause of absence from school. If parents have asthma, their children are more likely to develop the disease. Children in homes where an adult smokes are more at risk. It is important to find out the _ for asthma. As we know, dust, pollen, or animals often make people suffer from asthma. Once a child learns the triggers, he can help prevent future attacks. About half of all children outgrow asthma and then asthma attacks stop when they are teenagers. However, many people live with the disease into adulthood. Children often take control drugs once or twice a day to help prevent asthma attacks, if a child begins to have an asthma attack, a quick-relief drug is also necessary. This is often an inhaler. School-aged children usually carry their inhalers with them. This medication works quickly and children begin to breathe more easily in a few minutes. If a child has a serious asthma attack, he may need full-time care at a hospital or a doctor's office. The story of Rick Garcia is used to   _  .
show the importance of exercise introduce the topic of the text show the popularity of soccer tell us how to control asthma