Final answer:
The correct verb form to complete the sentence is 'comprábamos'.
Step-by-step explanation:
The verb form that correctly completes the sentence is comprábamos.
In this case, the subject is 'nosotros,' which means 'we.' Since 'comprábamos' is the conjugated form of the verb 'comprar' (to buy) in the past tense, it matches with the subject 'we.'
An example sentence would be: 'Usualmente nosotros comprábamos revistas de finanzas.'
Learn more about verb conjugation in Spanish