In French, the correct form of the verb "manger" (to eat) to use in this sentence is "mangez" because the subject "Vous" (You, formal or plural) requires the second-person plural conjugation of the verb. Therefore, the sentence translates to "You (formal/plural) eat a sandwich." The conjugations "mange," "manges," "mangeons," and "mangent" are for different subjects and do not match with "Vous." "Mange" is for the third-person singular, "manges" is for the second-person singular, "mangeons" is for the first-person plural, and "mangent" is for the third-person plural.