Final answer:
The appropriate form of the verb gustar is gustaban.
Step-by-step explanation:
The appropriate form of the verb gustar to fill in the blank in the sentence is gustaban. The sentence reads, 'Recuerdo que, cuando Ana era pequeña, a ella no le gustaban naranjas.' In this sentence, 'gustaban' is used because it agrees with the plural noun 'naranjas'.
Learn more about Verb conjugation in Spanish