Final answer:
The correct form of the verb 'deber' is 'debes'
Step-by-step explanation:
The correct sentence should be:
Tú debes beber más agua.
The verb deber means 'to should' or 'to have to' in English. In this sentence, it is conjugated to the second person singular form 'debes' to match the subject 'tú', which means 'you' in English. So, the complete sentence would be 'You should drink more water'.
Learn more about Conjugation of the verb 'deber'