The answer is A because it makes the most sense.
Question 8 - Tú estás escuchando a la profesora.
Question 9 - Nosotros estamos escribiendo cartas.
Question 10 - Marta está comiendo en el comedor.
Question 11 - Ellos no están pagando por el boleto.
Question 12 - Yo estoy hablando con Miguelito.
Question 13 - Ellos estaban mirando la televisión.
Question 14 - Nosotros estábamos viviendo en San Diego.
Questions 8 to12 are in the present progressive, which means that they refer to situations that are currently taking place. The present progressive is formed by the verb “estar” plus the gerund. Questions 13 and 14 are in the past progressive, which means they refer to situations that were taking place at a certain time in the past. Many times that action gets interrupted by some other action also taking place in the past. The past progressive is formed by the verb estar in the imperfect plus the gerund.