What were the killing fields of the khmer rouge?

Khmer rouge are the sites of Cambodia who witness killing and burying millions of people because of Execution, famine and forced labor during Khmer rouge regime led by Pol Pot hence known as killing fields of Khmer Rouge from 1975 to 1779. This period was termed as Cambodian holocaust of Cold war era where Pol Pot overtook the power at the end of Cambodian civil war and rightly described as genocidal tyrant of Cambodia

answer; i believe it was by president pranab mukherjee or by the chief justice of kerala high court; ///plz check luck

answer; i do believe its (b) 12.5 years of age;