The correct answer is: "fuimos" .
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Note the Spanish word: "ayer" (meaning "yesterday" ; so we used the "past (preterite) tense" of the Spanish verb, "ir" (to go); that corresponds with the subject pronoun in the given sentence—which is: "Nosotros" (first person, plural; meaning: "we"; and the correct, corresponding Spanish conjungation is: "fuimos" ; which means "[We] went".
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