Final answer:
The correct sentence that means "It was interesting." is "Fue interesante."
Step-by-step explanation:
The correct sentence that means "It was interesting." is Fue interesante. In Spanish, the past tense of the verb "ser" (to be) is "fue". So, to say "It was interesting." you would say "Fue interesante." The verb "ir" (to go) is not used to express the idea of "interesting", so the correct answer is not based on the conjugation of "ir".
Learn more about Spanish verbs