The answer is A, because you are always "saying" the truth
Answer : A) tengo catorce años.
¿Qué edad tienes? Tengo catorce años.
Spymore
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.
