Rule reminder
Sequence of tenses with present main clause: (1) Main clause PRESENT + subordinate action SIMULTANEOUS or FUTURE → present subjunctive. (2) Main clause PRESENT + subordinate action PRIOR (already happened) → congiuntivo passato (present subjunctive of avere/essere + past participle). Example: 'Credo che studi' (I think he is studying now) vs 'Credo che abbia studiato' (I think he studied already).
It is possible that she already left the office. Choose the correct form: 'È possibile che _____ già dall'ufficio.'