How did soviet leaders spread the communist message effectively?

here are the choices:

a. by creating an atmosphere of free speech to encourage people to explore communist ideology

b. by terrorizing people and forcing them into concentration camps if they opposed the revolution

c. by using the minority ethnic groups in the soviet union to communicate the message broadly

d. by using bold, attractive posters to create a popular culture around the party’s ideology

the answer is d. by using bold, attractive posters to create a popular culture around the party’s ideology