III. Complete the sentences with am, is or are.
1.         A: Where's Jack?
        B: He          playing football.
2.         A: Let's 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 isn't at home. She                  riding her bike.