Final answer:
The correct imperfect tense form of the verb 'gustar' to complete the sentence is 'gustaba'.
Step-by-step explanation:
The correct imperfect tense form of the verb gustar to complete the sentence is gustaba.
The sentence should be: Cuando era pequeña, a Marisa le gustaba la clave.
In Spanish, gustaba is used to express likes or preferences in the past. The verb gustar is conjugated to match the subject, in this case, 'Marisa'.
Learn more about Spanish verb conjugation