Right answer:
A mí me gusta estudiar mucho en la escuela
An Indirect Object Pronoun is a person that receives the action of a verb indirectly. Its purpose is to tell you to whom or for whom something is done. So in this sentence the action is being performed for me, that's why we choose the indirect object pronoun for the first person singular, which is me. On the other hand, since after the second blank comes an infinitive verb, then we need to conjugate the verb gustar for the third person singular in the simple present, which is gusta. Finally:
A mí me gusta estudiar mucho en la escuela