Answer for me please thank you:)

Which statement best describes a major advantage of a confederal system of government over a unitary system

Why did win shihuangdi force all nobles to live at the capital?

Why was the united states motivated to establish the open door policy? a. the policy guaranteed american commerce with china. b. the policy supported the chinese nationalist cause. c. the policy led to a gain of american colonies in asia. d. the policy claimed damages from the chinese.