Final answer:
The verb 'terminar' should be conjugated in the preterite tense as 'terminé' to match the past action of completing the exam.
Step-by-step explanation:
Por fin, yo terminé este examen.
In this sentence, the verb 'terminar' should be conjugated in the preterite tense to match the past action of completing the exam. Since the subject is 'yo' (I), the appropriate form is 'terminé', which is the first person singular conjugation of the verb in the preterite tense.
Learn more about Conjugation of the verb 'terminar' in the preterite tense