One Good Argument That Attempts to Justify Killing in Defense

One good argument that attempts to justify killing in defense of the innocent says that

A) the good of defending the innocent outweighs the bad of killing a person threatening to kill innocents.
B) the good of killing a person threatening innocents is at least equal to any bad.
C) God works in mysterious ways and humans don't understand His morality.
D) we must defend the innocent to the point of killing those who threaten them because it's justice.