The correct answers are B) the U-2 incident, C) the first test of a Soviet atomic bomb, C) the Sputnik launch.
The events that added to Americans’ fear of attack by the Soviet Union were the U-2 incident, the first test of a Soviet atomic bomb, and the Sputnik launch.
Those wear the tense years of the Cold War in which the Soviet Union competed in the arms race and later in the space race. The world lived tense moments that were at its peak during the Cuban missiles crisis of 1962, where the world was on the brink of another war.
After the United States knew about the first test of a Soviet atomic bomb, the government set the alarms. Then, when the USSR sent the first satellite -the Sputnik- into space, the federal government knew that the risk of an attack was more because the Soviet Union could steal critical information about the US security and intelligence. After the U-2 incident, there was no doubt that an attack was a real option.