Use "I", " you", "he", " she", "am", " it", "we" or "they"
1. ... is a doctor,and ... am a vet.
2. This is out house. ... is very nice and comfortable.
3. What's this? ... is my cat, ... is not very friendly.
4. How are ...? - ...'m fine,thanks. And ...?
5. Meet Tom and Betty, ... are my best friends.
6. ... am a first year student. ... am very happy.
7. My sistet is a teacher. ... is thirty years old.
8. ... are a very happy family.

 1. she, i2. it3. it, he4. you, i, you5. they6. i, i7. she8. we

1.He is a doctor,and I am a vet. 2. This is our house.It is very nice and comfortable. 3. What's this? It is my cat, it is not very friendly. 4. How are you? - I'm fine,thanks. And you? 5. Meet Tom and Betty, they are my best friends. 6. I am a first year student. I am very happy. 7. My sister is a teacher. She is thirty years old. 8. We are a very happy family.