The correct option is "people began to seriously question communism."
The Cultural Revolution, also known as the Great Proletarian Cultural Revolution, was a sociopolitical movement that took place in China from 1966 to 1976. Initiated by Mao Zedong, then leader of the Chinese Communist Party, his stated goal was to preserve Chinese communism by reusing the remnants of capitalist and traditional elements of Chinese society, and reimpose the thought of Mao Zedong (known outside of China simply as Maoism) as the dominant ideology within the Party. The Revolution marked the return of Mao to a position of power after the failures of his Great Leap Forward. The movement paralyzed China politically and negatively affected both the economy and the country's society to a significant degree.