¿Vosotros os cepilláis los dientes todos los días?
<u>Explanation</u>:
Remember that reflexive verbs need a <u>reflexive pronoun</u> to use (me, te, se, nos, os). It depends on who the verb falls to, a different reflexive pronoun will be used. As the verb "<u>cepillarse</u>" is reflexive, they must be added after the verb when the form of the verb is impersonal (infinitive, gerund and participle).
In this case, the pronoun is "vosotros/as" (you) so the reflexive pronoun is "os".
<h3><em><u>MissSpanish</u></em></h3>