Respostas

2014-08-26T19:56:01-03:00
I am not a teacher
You are not (aren't) my best friend
He is not (isn't) a doctor
She is not (isn't) my mother
It is not (isn't) raining
We are not (aren't) brothers
You are not (aren't) sisters
They are not (aren't) my parents
2014-08-26T20:08:33-03:00
A) I don't am a teacher
b) You don't are my best friend
c) He doesn't is a doctor
d) She doesn't is my mother
e) It doesn't a rainning
f) We don't are brothers
g) You don't are sisters 
h) They don't are my parents

Você usa o auxiliar do not ou doesn't para colocar na forma negativa, o doesn't é mais formal, na 3ª pessoa vc coloca Doesn't que são He, She e It e nas demais vc coloca Don't.
Espero ter ajudado!