Last week I caught a cold. My sister kept saying the cold was caused by both the ice pop I ate and the heat. She and I went out for noodles on a hot day. I sweated a lot and bought an ice pop to cool myself down. About 40 hours later， I started to sneeze and had a fever. Her idea was based on Chinese medical theory about “han”-cold and “re”-heat. It says that if you suddenly eat something cold on a hot day， you will catch a cold.
　　I find that idea not true. Modern science shows that colds are caused by a virus. On that day， we spent a couple of hours with a friend who had a cold. She was coughing all the time we were together. I probably got the virus from her. Once you get the cold virus， it stays in your body. You can’t kill it. Your body recovers and the virus calms down and goes to sleep. The virus lives with you and changes with you. Once a while， it wakes up to stimulate your immune system.
　　There were other people eating ice pops and walking on that hot day. They didn’t have a cold. Others stayed in the cool air conditioned rooms and went out into the heat， they were fine. Why？ That’s because they were not exposed to the virus.
　　Chinese medical theories are believed by many people， but I think western science makes more sense.
　　Vocabulary
　　virus n. 病毒
　　stimulate v. 刺激
　　（What do you think caused the cold？）