Final answer:
The correct verb phrase to complete the sentence is estarán.
Step-by-step explanation:
The correct verb phrase to complete the sentence is estarán. This is because the subject of the sentence is 'ellos', which is the third person plural, and the verb 'estar' needs to agree with the subject in number and person. The correct conjugation for 'estar' in the future tense, third person plural, is 'estarán'. Here is an example: 'El próximo mes ellos estarán revisando los textos para corregir errores gramaticales y de lenguaje.'
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