Do e don't são usados com os pronomes I, you, we, you e they e does e doesn't são usados com he, she, e it.
A resposta então, seguindo essa regra ficaria assim:
a) I don't know the answer.
b) Most trees don't grow very quickly.
c) Doesn't Sara understand this?
d) Do you want talk about it?
e) The price doesn't Include service.
f) Do you remember me?
Bons estudos
