Answer:
1. A: Look! My classmates Maria and Teresa!
B: (1) Are they Mexican?
A: No, they (2) aren't. They (3) are Peruvian.
2. A: That’s my friend Jerry.
B: (1) Is he a firefighter?
A: No, he (2) isn't . Barry (3) is a firefighter. Jerry (4) is a police officer.
3. A: (1) Are you a new student?
B: Yes, I (2) am. My name (3) is Brian.
A: (4) Are you from Australia? B: No, I (5) 'm not. I (6) 'm from the U.K.
Explanation:
In the Present Simple, the verb to be has three forms for the different subject pronouns:
I --> am
She / he / it --> is
We / you / they --> are
In that matter, the negative form of am, is and are are am not or 'm not, is not or isn't and are not or aren't, respectively. Besides, in the interrogative form there is inversion of the verb to be, so that am, is and are are located before the subject.
