Final answer:
The verb form 'estudiábamos' is the correct choice.
Step-by-step explanation:
The correct verb form to complete the sentence is estudiábamos.
'Nosotros' is the subject of the sentence, which means 'we' in Spanish. The verb form 'estudiábamos' agrees with the subject and means 'we studied' in English.
For example, the complete sentence would be:
'Nosotros estudiábamos juntos en la biblioteca de la escuela.'
Learn more about Spanish verbs