The correct answer is B. Information provided by spies in the United States.
Step-by-step explanation
During World War II, several of the world powers began to experiment with nuclear weapons, which triggered an extensive study in this field. This practice allowed what is known as nuclear espionage to occur, which was a practice used by some countries to pay the scientists who investigated in these studies to obtain information that would allow them to develop better nuclear weapons than their adversaries. In the case of the Soviet Union, it was Klaus Fuchs who stood out in this task of spying on the Manhattan project of nuclear development of the United States, Canada, and Great Britain, which allowed the Soviet Union to develop nuclear weapons. So, the correct answer is B. Information provided by spies in the United States