阅读短文，回答问题。 It's four o'clock in the afternoon . Mr Chen and his students are in the playground. They are having a PE lesson. Mr Chen: Boys and girls, let's do some exercise first. Students : Yes, Mr Chen. Mr Chen: Put your hands on your head and put your feet together. Jump up and down fifteen times. Ready, go ! Yang Li: Sorry , Mr Chen. I can't. Mr Chen : What's wrong with you , Yang Li? Yang Li: I've got a bad stomach ache. Mr Chen: I'm sorry to hear that. Do you want to see a doctor? Yang Li: No, I don't. Mr Chen: OK. I can get a chair for you. You can sit over there and have a rest. Yang Li: Thank you, Mr Chen. Mr Chen: Not at all.  (to the other students) Boys and girls, let's go on with our lesson. Students: OK. 1. Where are the students? 2. What are they doing? _ 3. Can Yang Li do any exercise? _ 4. What's the matter with her? _ 5. Does she want to see a doctor? _