Final answer:
The appropriate indirect object pronoun to fill in the blank is "A. nos".
Step-by-step explanation:
The appropriate indirect object pronoun to fill in the blank in the sentence "A nosotros ______ gustaba Jugar en el césped" is A. nos. In Spanish, indirect object pronouns are used to replace the nouns that receive the action indirectly.
Learn more about Indirect object pronouns in Spanish