Tell what time it is(es la/son las) at each point in the day. 25points

Choose the most appropriate demonstrative adjective and complete the following sentences.estalesa carta que estoy escribiendo es para mi abuelita.

Okay so i'm taking an online spanish course (penn foster), and in the study guide, you have to create a bunch of sentences with words you've learned so far. translating, reading, and those kinds of things are fairly easy, but when it comes to making my own sentences, my brain just kinda waltz's away. anyone got any tips?

El estudiante leía una novela de terror cuando, de repente, alguien _ a su puerta a. llamé b. llamó c. llamando d. llamaba