Final answer:
The appropriate verb to fill in the blank is 'sabes'
Step-by-step explanation:
The appropriate verb to fill in the blank in the sentence '¿tú jugar al tenis?' is 'sabes'.
In Spanish, the verb 'saber' means 'to know'. When addressing a single person, the correct form in this context is 'sabes'.
For example: '¿Tú sabes jugar al tenis?'
Learn more about Verb conjugation