The verb form that has changed its stem is "queréis." The verb "querer" (to want) undergoes a stem change in the present tense for certain forms, specifically in the second person plural (vosotros) where it becomes "queréis" instead of the expected form without the stem change. In this form, the stem "quer-" changes to "quer-" and the ending changes accordingly.
If the answer options intended to refer to a specific response option based on a typographical error, please clarify.