Answer:
The correct answer is Estás.
Explanation:
What we have here is the verb SER. In English, to express this verb we use the verb "to be", but the verb to be, in Spanish also means ESTAR.
SER is used to describe appearances, identity, family relationships, when and where an event takes place, time and date.
And ESTAR expresses a mood or health status, an aspect, the marital status of a person, their location.
Here is the complete conjugation of these verbs:
SER:
yo soy
tú eres
él/ella es
nosotros somos
ellos son
ESTAR:
yo estoy
tú estás
él/ella está
nosotros estamos
ellos están