Final answer:
The correct direct object pronoun to complete the conversation is 'las.' It represents the plural objects that were bought.
Step-by-step explanation:
The correct direct object pronoun to complete the conversation is las.
In the conversation, Eduardo says, 'Tuvimos que comprar muchas cosas,' which translates to 'We had to buy many things.' To respond, Victor would say 'Las compraste o no?' which translates to 'Did you buy them or not?'
The pronoun 'las' is used because 'cosas' is a feminine plural noun, and 'las' functions as the direct object pronoun representing the plural objects that were bought.
Learn more about Direct object pronouns in Spanish