Why Did China Attack American Forces in 1951

Multiple Choice

Why did China attack American forces in 1951?

A) MacArthur had pushed the North Korean military to China's border on the Yalu River.
B) Truman had cut off China's economic aid.
C) Eisenhower had placed naval ships in the Sea of Japan.
D) Stalin demanded that China prove itself as a supporter of Communism during the Cold War.