Question

passes as frazes abaixo para a forma negativa

a)I am a theacher

b)You  are my best friend

c)He is a coctor

d)She is my mother

e)It is rainning

f)We are broothers

g)You are sisters

h)They are my parensts

Answer 1

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

Answer 2

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!