<em>Carlos, ¿Se </em><em>acuerda </em><em>de cuando fuimos de vacaciones a Cancun hace dos años?</em>
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<h2>Explanation:</h2>
This question stands for reflexive pronouns. We use Reflexive Pronouns with a verb to point out that a person carries out an action to or <em>for himself</em> or <em>herself. </em>The action here is to remember something. Since a person is addressing the question to Carlos and uses se, then this matches the subject pronoun usted (formal you). Then the conjugation of acordar must match the third person singular, which is acuerda.
generlly speaking tu is used with people younger than or acquaintances/people that are close to you. While Ud. is used for the elderly and for people you show respect to
