I believe that it would be B (reloj) since it is talking about how there is a window, a door and then a clock in a classroom.
It is also giving you the masculine singular form indicating that it can only be reloj.
If it has a correct gender specific noun. If its singular or plural. Irregular verbs. The fact there is two different verbs. Past tense or current. Verb of change. Spanish prepositions. Direct and indirect pronouns. The word gustar.
Not sure but I do live in the Dominican Republic
