Final answer:
The appropriate form of the verb 'ser' to fill in the blank in the sentence 'Yolanda y yo ______ muy buenas amigas' is 'somos'.
Step-by-step explanation:
In the sentence 'Yolanda y yo ______ muy buenas amigas,' the appropriate form of the verb 'ser' to fill in the blank is 'somos.' This is because 'Yolanda y yo' is the subject of the sentence, which is the first-person plural pronoun in Spanish. The verb 'ser' conjugated in the first-person plural form is 'somos.'
Learn more about Conjugating the verb ser in Spanish