Final answer:
The appropriate verb to fill in the blank in the sentence ¿Cuántos años tú? is 'tienes'.
Step-by-step explanation:
The appropriate verb to fill in the blank in the sentence ¿Cuántos años tú? is option B. tienes. This is because the question is asking for someone's age, which is indicated by the verb 'to have' in Spanish. So, the sentence translates to 'How old are you?' and the correct verb for 'are' in this context is 'tienes'.
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