Ustedes is formal and should be used when talking to someone you’re not so familiar with, like a stranger, or someone that should be addressed with respect, like an elderly person.
Answer:
1) la
2) los
3) unos
4) las
Explanation:
1. "la" agrees with " clase"
2. "los" agrees with "libros"
3. "unos " agrees with "bolígrafos"
4. "las" agrees with "clases"
I hope this helped you. Have a great day! Remember to pay it forward. :)
Answer:
it doesn't let me post my answer so, answer is in the attachment