Question

Which of these helped the Soviet Union develop nuclear capabilities?

scientific data provided by Earth-orbiting satellites

information provided by spies in the United States

classified documents left behind by the U.S. military in Korea

plans provided to the International Atomic Energy Commission

Answer 1

I'd definitely go with the second answer, information provided by spies in the United States. Historians have reasoned that when Truman told Stalin that the US had a powerful weapon at one of their conferences, Stalin didn't seem surprised because he already knew about the atomic bomb project they were working on thanks to spies inside of it.

The other answers don't really work. The first satellites didn't have the kind of capabilities that would have helped push their nuclear projects forward and the US military didn't leave that kind of information just lying around during the Korean War. The IAEC is also not in the habit of sharing plans for nuclear weapons, either.