What Extremely Harsh Tactic Did the British Use to End

What extremely harsh tactic did the British use to end their war with the Boers in South Africa?

A) All Boer prisoners were brutally tortured, with most dying before they could be executed.
B) Captured Boer soldiers were transported to Australia.
C) The British forced Boer families into makeshift compounds known as concentration camps.
D) The British planted land mines in fields cultivated by the Boers.
E) The British poisoned wells used by the Boers.