Ann was ill. She went to see a doctor. The doctor asked her to1her tongue (舌头), and then he said,  "OK. You can put your tongue back now. There's2wrong with you, but I'm afraid you have a problem, you never do3"

    "But, doctor," Ann said, "I don't think so."

    "Don't4me what you think," the doctor said, "I see a lot of people5you. None of them get any exercise. They sit in offices all day and in front of the TV in the evening. You must walk quickly for at least 20 minutes a day."

    "Doctor, you don't understand," Ann said, "I take enough exercise every day."

    "I don't want to6any excuses," the doctor said, "You must spend time 7 exercise, if you don't, you will get8 and have health problems."

    "But I walk every day." Ann said.

    "Oh, yes, and I know what kind of walking that is. You walk9meters to the bus stop from your house, from the bus stop to your office, and from your office to your dining-room for lunch and back. That's not a real walk. I'm talking about a walk by the lake or in the park for 20 minutes every day."

    "Would you please 10  me, doctor?" Ann said,   "I'm a postwoman. I walk for nearly seven hours every day."

    For a moment the doctor was silent, then he said, "Can I see your tongue again?"

写出该化学反应的符号表达式：____

用when/while填空。