What is meant by "Bleeding Kansas"?

Question options:

Refers to the "open sore" caused by the vicious verbal debate over whether to be a free state or a slave state


Refers to the killing on all of the animals and livestock of slaveholders by supporters of a non-slave Kansas


Refers to the killing of all slaves in the Kansas territory by white slaveholders


Refers to open fighting between pro-slave and free-state supporters including burning of towns and massacres of people not fighting