Final answer:
The regular verb in the imperfect tense is 'hablaban'. It means 'The kings spoke with the prince.'
Step-by-step explanation:
The regular verb in the imperfect tense is 'hablaban' because it agrees with the subject 'Los reyes' in person and number, and it follows the regular -ar verb conjugation pattern. The sentence 'Los reyes hablaban con el príncipe' means 'The kings spoke with the prince.'
Learn more about imperfect tense