Answer:
Ellos eran tres amigos.
Explanation:
Because the sentence states that they WERE friends (imperfect conjugation), I expect that we should be conjugating the verb "ser" (to be).
Since the question states, "Ellos", we will be using the plural form (found on the last row of the diagram), which is followed by eran. This, of course, is the imperfect conjugation of the verb, instead of the present tense.
Hope this helps!
