Espero que nosotros __________________ al parque mañana.

“Espero que” expresses a wish or hope, so it is followed by the present subjunctive. The present subjunctive form of “ir” for “nosotros” is “vayamos,” making the sentence “Espero que nosotros vayamos al parque mañana” (“I hope that we go to the park tomorrow”). “Van” and “vamos” are indicative forms and do not fit this expression of hope.

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