Final answer:
The correct subject pronoun for the verb 'estoy' is 'yo' in Spanish.
Step-by-step explanation:
The correct subject pronoun for the verb estoy is yo. When using the verb estoy, which means 'I am', the subject pronoun 'yo' is the correct choice. For example, 'Estoy feliz' translates to 'I am happy'.
Learn more about Subject pronouns in Spanish