Final answer:
In this sentence, the correct verb form is 'duermo'.
Step-by-step explanation:
The correct form of the verb in this sentence is duermo.
The correct sentence is: Yo duermo ocho horas todas las noches.
The verb 'duermo' is the first person singular form of the verb 'dormir' (to sleep) in the present tense. It changes according to the subject of the sentence, in this case, 'yo' (I).
Learn more about verb conjugation