Ustedes is formal and should be used when talking to someone you’re not so familiar with, like a stranger, or someone that should be addressed with respect, like an elderly person.
A is the answer.. (cocinamos)
1) The uncle is brave
The uncle is not brave
2) I was tired and sick
I wasn’t tired and sick
3) She’s the aunt
She’s not the aunt
4) They are my family
They are not my family
5) She is regretting it
She is not regretting it