Final answer:
Legalism ended the Warring States Period by enabling Qin Shi Huang to unify China through strict laws and centralized control. Legalist reforms standardized laws, writing, and currency, and helped construct large state projects. However, the dynasty's harsh policies led to its rapid collapse after the emperor's death.
Step-by-step explanation:
The philosophy of Legalism played a significant role in ending the Warring States Period. The correct answer to the question of why Legalism ended the Warring States Period is A) Shi Huang Di forced people to obey government and forced people to work as one people under one ruler or be severely punished. Legalism, as propagated by thinkers like Shang Yang, established a system that maximized the power of the ruler, and its policies were instrumental in the rise of the Qin state. Legalist thought rejected the past as a model and focused on laws suitable for contemporary conditions to consolidate the Qin ruler's power. This approach differed greatly from other philosophical schools of the time, such as Confucianism and Daoism, which often looked back to a distant ideal past.
Once in power, Qin Shi Huang, or Shihuangdi, implemented Legalist reforms that fostered unity and streamlined the bureaucracy. Legalism in Qin resulted in the uniformity of laws, writing systems, and currency, bolstering the state’s control over its subjects. Its power and expansionism were also reflected in the construction of massive state projects like the Great Wall.
Nevertheless, the Qin dynasty's reliance on harsh Legalist policies carried the seeds of its own downfall, as the death of Qin Shi Huang was swiftly followed by revolts against the brutal and authoritarian regime, leading to the dynasty’s collapse. This highlights the brittleness of a state that is overly reliant on rigid enforcement of law without popular support.