Complete the sentences with am, is or are.
1. A :Where is Jack?
    B: He ........... playing football.
2. A: Let is play table tennis.
    B: Sorry. We ............. having dinner now.
3. A: Where are Linda and Kate?
    B: They ............... shopping.
4. A: Are you OK?
    B: Yes, I ........... having great fun.
5. A: Please help me.
    B: Sorry. I ............. reading a book.
6. A: Can I talk to Lan?
    B: She is not at home. She ............... riding her bike.