Final answer:
The sentence from the passage that best states the main idea is option A) "It was a massive show of force, an unmistakable warning to anyone who might dare oppose China's government."
Step-by-step explanation:
The sentence from the passage that best states the main idea is option A) "It was a massive show of force, an unmistakable warning to anyone who might dare oppose China's government." This sentence summarizes the main theme of the passage, which is the use of force by the Chinese government to suppress protests and dissent.