Sarah was ill, she went to see the doctor.   " Doctor, I'm not feeling well," she said. " Every time I do my homework, I feel tired. If I go to school on foot, I have to sit down and rest for ten minutes." The doctor looked at her carefully. At last he said, " Nothing much. But I'm afraid you are eating too much."  "I don't understand, what do you  mean ? "asked Sarah. "I mean you eat too much food," said the doctor.   " Oh! You mean I'm too fat. That's a problem." Said Sarah. "What should I do If I don't want to be heavy !"  " The answer is easy," said the doctor. " If you want to be thin and healthy, you shouldn't eat a lot of food and you also should do much exercise." Sarah went to school   _   .
by bike by bus by car on foot