How did Soviet leaders spread the Communist message effectively?

Responses
by using the minority ethnic groups in the Soviet Union to communicate the message broadly
by creating an atmosphere of free speech to encourage people to explore Communist ideology
by using bold, attractive posters to create a popular culture around the party’s ideology
by terrorizing people and forcing them into concentration camps if they opposed the revolution

The correct response is:

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