Final answer:
The correct sentence in Spanish to express eating pizza once a week is 'Yo como pizza una vez a la semana'.
Step-by-step explanation:
The correct sentence would be: Yo como pizza una vez a la semana. In this sentence, the subject 'yo' (meaning 'I') is followed by the verb 'como' (meaning 'eat') conjugated in the first person singular form. 'Pizza' is the direct object, and 'una vez a la semana' means 'once a week'.
Learn more about Expressing frequency of an action in Spanish