[单选题]The paragraph is followed by an incomplete phrase or sentence which summarizes the main idea of the paragraph. Choose the missing words of the phrase or sentence.


It is not murder to kill someone with lawful excuse; lawful excuses include killing enemy combatants in time of war (but not after they surrendered), killing a person who poses an immediate threat to the lives of ones self or others (i. e. in self-defence), and executing a person in accordance with a sentence of death (in those jurisdictions which use capital punishment). Sometimes extreme provocation or duress can justify killing another as well. These cases of killing are called justifiable homicide.

（） of reseanable killing.