Question

how did soviet leaders spread the communist message effectively?
by using bold, attractive posters to create a popular culture around the partys ideology
by creating an atmosphere of free speech to encourage people to explore communist ideology
by terrorizing people and forcing them into concentration camps if they opposed the revolution
by using the minority ethnic groups in the soviet union to communicate the message broadly

Explanation:

Soviet leaders used bold and attractive posters to promote Communist ideology and create a popular - culture around the party. This was a common propaganda method. Creating an atmosphere of free - speech was not a main way as the state had a controlled information environment. Terrorizing people and concentration camps were not for spreading the message but for dealing with opposition. Using minority ethnic groups to spread the message broadly was not the main effective method for spreading Communist ideology.

Answer:

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