Final answer:
The regular verb in the imperfect tense is 'Las hadas leían hechizos'.
Step-by-step explanation:
The correct option with the regular verb in the imperfect tense is: Las hadas leían hechizos. In this sentence, the verb 'leían' is in the imperfect tense. The imperfect tense is used to describe ongoing or repeated actions in the past. In contrast, the other options 'Las princesas van al jardín' (present tense), 'Las princesas hablaron con los príncipes' (preterite tense), and 'Las hadas compraron un huso' (preterite tense) do not use the imperfect tense.
Learn more about Imperfect tense in Spanish Verbs