Rule reminder
Sequence of tenses with past main clause (passato prossimo, imperfetto, passato remoto, or conditional): (1) Subordinate action SIMULTANEOUS with past main action → imperfect subjunctive (congiuntivo imperfetto). (2) Subordinate action PRIOR to past main action → past perfect subjunctive (congiuntivo trapassato: imperfect subjunctive of avere/essere + past participle).
The professor thought the student was cheating during the exam. Choose the correct form: 'Il professore pensava che lo studente _____ durante l'esame.'