The correct answer is 'gustaba.' It is the imperfect conjugation of 'gustar' used to match the subject Gloria in expressing 'liked' in the imperfect tense.
The correct answer is: gustaba.
In this sentence, gustaba is the correct imperfect conjugation of the verb gustar to match the subject Gloria and convey the meaning 'liked' in the imperfect tense.
Remember, in Spanish, the verb gustar is conjugated differently as it is used with an indirect object pronoun to indicate who likes something.