The correct phrase to complete the conversation is 'sea muy fuerte,' meaning 'is very strong.'
The correct answer is: C. sea muy fuerte. In the conversation, Person A is asking why Cristóbal cannot be part of the football team, which implies a physical ability requirement. Saying 'No creo que él sea muy fuerte' indicates that Person B believes Cristóbal might not be strong enough for the team.
https://brainly.com/question/38073430