What two eastern bloc nations tried to break away from the soviet union in the 50s and 60s, only to be crushed?

Hungary and Czechoslovakia attempted to leave the Eastern Bloc during the 1950s and 1960s. In 1956, Hungary experienced a revolt against the Hungarian government and the Soviet policies put into place. This was a student-led revolt spread quickly leading to an overthrow of the government. The new government wished to leave the Warsaw Pact and was willing to negotiate Soviet soldiers being released from the nation. However, the USSR choose to crush the revolutionaries and install a new Soviet regime. 
In Czechoslovakia, liberal reforms began in the 1950s. By 1968, a liberalist leader had been elected who began to roll back Soviet policy. The Warsaw Pact members invaded Czechoslovakia and overthrew the government again installing a more pleasing communist regime. 

Your answer should be choice b!