The correct verb form to complete the sentence is "debes." Here's why:
1. In Spanish, verbs need to agree with the subject of the sentence in terms of person and number. In this case, the subject is "Tú" (You), which is singular second person.
2. The verb "debes" corresponds to the singular second person form of the verb "deber" in the present tense. This means "Tú debes" translates to "You must" or "You should."
3. The verb form "debe" (without the -s) is the third person singular form, which would not agree with the subject "Tú."
Therefore, the correct answer is "O A. debes."
