Ответ:

1 Susan is new to the school.

Susan isn't new to the school.

Ответ: isn't

2 I am 14 years old.

I am not 14 years old.

Ответ: am not

3 They are in Room E.

They aren't in Room E.

Ответ: aren't

4 He is my best friend.

He isn't my best friend.

Ответ: isn't

5 You are in Grade 7.

You aren't in Grade 7.

Ответ: aren't