What Is the "Responsibility to Protect" Norm in World Politics

What is the "responsibility to protect" norm in world politics?

A) The idea that military only exists to protect the sovereign capacity of a state
B) The idea that war is only acceptable in response to an unprovoked attack on a state's own territory
C) The idea that states can protect their own borders and citizens through preemptive action
D) The idea that states must sometimes intervene when other states are failing to shield their citizens from mass atrocities