Which of the Following Statements About Tibet Is True

Which of the following statements about Tibet is true?

A) The Soviet Union invaded Tibet after the Chinese Revolution.
B) China has no historical claim to Tibet.
C) China invaded Tibet,and the United Nations took no action to repel the attack.
D) China invaded Tibet,and the United Nations sent troops in an attempt to repel the attack.
E) North Korea helped China invade Tibet after the Korean War.