Final answer:
The subject pronoun 'nosotros' correctly completes the sentence 'We are friends' in Spanish.
Step-by-step explanation:
The subject pronoun that correctly completes the sentence 'We are friends' in Spanish is nosotros.
'Somos amigos' is the correct translation of 'We are friends' in Spanish. The subject pronoun 'nosotros' represents 'we' in the sentence, so it is the correct choice.
'Ellas' is the subject pronoun for 'they' when referring to a group of all females, and 'ustedes' is the subject pronoun for 'you all'. These pronouns would not be appropriate in the given sentence.
Learn more about Subject pronouns in Spanish