Answer:
a. celebraron
Step-by-step explanation:
[] Ellos is a group of people (meaning "they" masculine)
-> In Spanish, when you change an infinitive (celebrar in this case, an infinitive is a verb ending in ar, er, or ir) the ending depends on the pronoun (I, you, me. In this case it is ellos)
[] Each pronoun has a number associated to it, 1 through 5. There is also the pronoun vosotros/vosotras, but those are more common to Spain so it depends.
-> Yo is 1
-> Tú is 2
-> Usted, Èl, and Ella are 3's
-> Nosotros/Nosotras is 4
-> Ustedes, Ellos, and Ellas are 5's
This means that Ellos is a 5.
[] There are 5 different Spanish endings for all verb tenses. See where I am going with this?
-> Using this method you can quickly conjugate many verbs for all pronouns.
Yo celebré
Tú celebrate
Usted/Èl/Ella celebro
Nosotros/Nosotras celebramos
-> Ustedes/Ellos/Ellas celebraron <-
Have a nice day! Everyone is taught Spanish differently, but I hope this will make sense to you
I hope this is what you are looking for, but if not - comment! I will edit and update my answer accordingly.
- Heather