Why Did Yuri Gagarin Cause Great Concern in the United

Why did Yuri Gagarin cause great concern in the United States?

A) He organized the Soviet missile program and threatened to "bury" the West during a visit to the United States.
B) He was the first man to orbit the earth, thus demonstrating that the Soviet Union was ahead of the United States in space technology.
C) He was the chief scientist on the Soviet nuclear weapons program during the cold war.
D) He was the director of the KGB, the Soviet intelligence agency responsible for spying on the United States.