Respuesta :

wuzzleluver
sont arrivées 


This is because "arriver" is a MRS. VANDERTRAMP verb. meaning that it conjugates with être in the perfect tense.

Here is a list of the MRS. VANDERTRAMP  verbs:

Montre
Retourner
Sortir

Venir
Arriver--- arrivé + es(because you are conjugating for "elles")
Naître
Desendre
Entrer
Rester
Tomber
Rentrer
Aller
Mourir
Partir

Bonne Chance!
I'm not sure what verb tense you wanted, but since there's two blanks to fill, i thought you would want it to be in passé composé.

The answer is "sont arrivées."