Final answer:
The correct verb form to complete the question is 'tienes'.
Step-by-step explanation:
The correct verb form to complete the question is tienes.
The word '¿Cuántos años?' is asking 'How old are you?' In Spanish, to say 'I am' you would use the verb 'tener' which means 'to have'. The correct form of 'tener' for 'you' is 'tienes'.
Example:
¿Cuántos años tienes? (How old are you?)
Tengo 15 años. (I am 15 years old.)
Learn more about Verb forms in Spanish