Question

I really need help finishing this, so please help me.. Why did the passing of atomic secrets to the Soviet Union by the Rosenbergs represent a significant threat to the United States? It meant that the Soviet Union would be able to make a direct nuclear attack on the U.S. mainland. It meant that the Soviet Union would be able to develop defenses to stop U.S. nuclear attacks on Soviet territory. It meant that the United States would no longer be the only nation on earth with control over atomic weapons.