Final answer:
The most appropriate form of the verb to fill in the blank is 'di'.
Step-by-step explanation:
The most appropriate form of the verb to fill in the blank is di. The correct sentence is 'Marta les dio las Invitaciones a sus amigos ayer.'
In this sentence, the subject 'Marta' is performing the action of giving the invitations to her friends. Since 'Marta' is a singular third-person noun, the correct conjugation of the verb 'dar' (to give) is 'dio'.
For example:
- Marta les di un regalo a sus amigos ayer. (Marta gave a gift to her friends yesterday.)
Learn more about Verb conjugation in Spanish