Sandra: ¿Dónde está Diego? Estamos esperándole desde hace una hora. Carolina: He recibido su mensaje. Dice que ___________________.
Translation:
Sandra: Where is Diego? We have been waiting for him for an hour.
Carolina: I have received his message. He says [blank].
The options:
va a llegar pronto - "he will get here soon"
está harto - "he is fed up"
está en camino - "he is on his way"
está de acuerdo - "he is in agreement"
está de moda - "it is fashionable"
We can safely eliminate options 2, 4, and 5 (whether Diego is fed up is immaterial; there is no information about opinions here, nor is there any mention of fashion - none of these details are relevant to the situation).
That leaves options 1 and 3. Upon closer inspection of the grammar, option 1 is not correct; the correct conjugation would llegará (llegará pronto), not va a llegar. The remaining option is correct.
Answer:
Carolina: He recibido su mensaje. Dice que está en camino.