Final answer:
The correct form of the verb ser for the given subject 'I' is 'soy' in Spanish.
Step-by-step explanation:
The sentence 'las tres y cuarto de la mañana' is an incomplete sentence. In order to complete it, we need to add a subject and a verb. Since the subject is 'I', we need to use the correct form of the verb ser to match it. 'I' in Spanish is 'Yo' and the correct form of the verb ser for 'Yo' is 'soy'. Therefore, the complete sentence would be 'Yo soy las tres y cuarto de la mañana'.
Learn more about Spanish verbs