The correct answer is option C - Armenian, Holocaust, Cambodian, Darfur.
Armenian - it was the extermination of 1.5 million Armenians during and after World War I, in 1915.
Holocaust - it was the extermination of some 6 million European Jews between 1941 and 1945 by the German Nazi.
Cambodian - A communist group known as the Khmer Rouge, led by Pol Pot seized control of Cambodia killing 1.8 million people by 1975.
Darfur - it was the first genocide of the 21st Century. Almost 400.000 Darfurists died by 2004.