B. que es esto? is the wrong one
I know for sure that its wrong, but sorry im not sure how to fix it.
The verb estar is an irregular verb, that means, it does not follow the pattern of all other "regular" -AR verbs.
The verb estar means "To Be" for temporary characteristics.
Think LCP (Large Cheese Pizza)
L- Location
C- Condition
P- Participle.
Those are when you use estar.
Conjugations of estar:
I am yo estoy
you are(Informal) tu estás
he/she is / you are(Formal) el/ella está // ud. está
We are nosotros estamos
You all are (spain only) - Vosotros Estáis
They are Ellos/Ellas/Uds. Estan
Sentence: I am happy today
Yo estoy feliz hoy
Incorrect the correct one is ( ¿Qué día es mañana?)
Nosotros comemos en la mesa.
millonarios o billonarios