Read the text and choose the correct forms of the verb to be.

My name's Brenda and I'm from the USA. I'm twenty-three years old and I'm a singer. My best friend's Kate. She's from Canada. Kate's 25 years old and she's a teacher. She's a very good teacher. Kate's sister's Mandy and her brother's Jack. Mandy's 18 and Jack's 19. Mandy and Jock are students.
They're very nice. We're all good friends.
1) Brenda ... a singer.

2) Jack ... 14 years old.

3) Brenda and Mandy ... sisters.

4) Mandy ... Jack's sister.

5) Jack ... Brenda's brother.

6) Kate and Jack ... brother and sister.