The transition from 4º ESO to 1º Bachillerato is jarring. In ESO, you might have learned that a subject is "who does the action." In 1º Bachillerato, that definition is legally void.
Also, special mention goes to ( Oraciones Pasivas Reflejas ). Trying to distinguish a "Pasiva Refleja" from an "Impersonal Refleja" has caused more existential crises in 16-year-olds than any philosophy class. ejercicios sintaxis 1 bachillerato