Final answer:
The correct verb to complete the sentence is 'fuimos'.
Step-by-step explanation:
The subject of the question is Spanish. The student is being asked to choose the correct verb to complete the sentence 'Nosotros (blank) a la biblioteca ayer.' The correct answer is option C. 'fuimos' because it is the conjugated form of the verb 'ir' (to go) in the first person plural (we) past tense (preterite). This option is appropriate because it matches the subject 'nosotros' ('we') and indicates the action of going to the library in the past.
Learn more about Spanish verb conjugation