Which source would be the best choice to support a rearach per on the evolution of baseball in the undyid states

Which of these did the soviet union do in 1961? it built a wall through berlin to keep people from moving to the west. it used force to destroy a wall the united states had built in berlin. it convinced the british and french to merge their zones in berlin with the soviet zone. it threatened to bomb berlin if the united states did not leave within 30 days.