What does King mean when he says, "Injustice anywhere is a threat to justice everywhere"?

A. If someone commits an unjust act anywhere within a state, then there is a risk of unjust acts being committed elsewhere in the state, but nowhere else.
B. If people commit crimes in one state, then it is more likely that crimes will be committed in other states.
C. When unjust acts are tolerated in one place, there is a danger that similar acts will occur and be tolerated elsewhere.