Answer:
D. hablar con la boca llena
Step-by-step explanation:
Which phrase best completes this sentence? Es de mala educación hablar con la boca llena
Which translates as "It's bad education talking when your mouth is full".
This is the only bad thing among the choices A,B,C,D. All the others represent good manners:
A. compartir la comida con los demás : share your food with others.
B. permanecer en la mesa hasta que todos acaben de comer : stay at table until everyone is finished eating.
C. esperar hasta que todos tengan la comida servida para empezar a comer: wait until everyone is served before starting to eat.
I hope this helps you.