Final answer:
The appropriate verb in the future tense to fill in the blank is 'harán'
Step-by-step explanation:
The correct verb in the future tense to fill in the blank in the sentence is harán.
This verb is conjugated in the third person plural ('ellos') and future tense ('harán'), which translates to 'they will do' in English.
For example, 'Ellos harán muchas cosas buenas' means 'They will do many good things'.
Learn more about Verb conjugation in Spanish