Answer:
es
Explanation:
because
when you use etre
it is subject pronoun + auxillary + past participle
so elles is Sp sont is auxillary the past pariciple for ir = i (e) (s)
so elles sont + root of sortir (infitive) is sort
then add i
then add e because it is feminine
and add s because it is plural
answer= elles sont parties