Although James Madison Was Initially Opposed to the Addition of a Bill

Although James Madison was initially opposed to the addition of a bill of rights to the Constitution, why did he subsequently support the proposal?

A) because of his pragmatic recognition of political realities
B) because of his unwavering adherence to political principles
C) because of his distrust that the system of checks and balances would actually work
D) because of his close friendship with Alexander Hamilton, who desperately wanted the Bill of Rights