Answer:
conjugation is very important in Spanish because verbs can change their form to match the subject of the sentence. For most verbs, there are six different form you could use depending on the subject the verb is paired with!
It would be "las" because sillas is feminine and it is plural. Las sillas
2. Yo me siento cansada en el entrenamiento
3. Mis amigos y yo nos reímos mucho en la competencia de patinaje
4. Los jugadores no visten el uniforme