Final answer:
The imperfect form of the verb in the sentence is correct.
Step-by-step explanation:
The imperfect form of the verb in the sentence "Éramos una hermosa tarde de verano." is correct.
The verb "éramos" is the first person plural form of the verb "ser" in the imperfect tense which means "we were". This verb form agrees with the subject pronoun "nosotros".
The sentence can be translated as "We were a beautiful summer afternoon."
Learn more about Imperfect verb form in Spanish