The response that BEST describes the way Qin Shi Huangdi unified warring nations is:
He set up a strong central government.
Qin Shi Huangdi, the first emperor of China, is known for establishing a centralized bureaucratic system that helped unify the various warring states under a single authority. Through this strong central government, he implemented uniform laws, standardized weights and measures, and centralized control over military and civil matters.