What caused the massacre of protesters in China's Tiananmen Square in 1989?

A. Protests by pro- and anti-communist citizens escalated into violence and required military intervention.

B. Mao Zedong wanted to publicly punish rural workers who resisted his "Great Leap Forward."

C. China's communist leadership refused to tolerate any mass demonstrations against the government.

D. Deng Xiaoping's attempted overthrow of the communist government resulted in violent resistance.