Select the option that can be used as a one-word substitute for the given group of words.
Crime of killing a king

* Regicide: The action of killing a king (from Latin rex meaning king + cidium meaning killing).
Pesticide: A substance used for destroying insects or other organisms harmful to cultivated plants or to animals.

Homicide: The killing of one human being by another.

Genocide: The deliberate killing of a large number of people from a particular nation or ethnic group with the aim of destroying that nation or group.