The correct option is C Indira Gandhi launched Operation Blue star in which many Sikhs were killed.
In the late 1970s and early 1980s, the Sikhs in Punjab started demanding for an independent country of Khalistan and began a movement which became violent and destructive. So Indira Gandhi launched Operation Blue Star in the Golden Temple at Amritsar. Many Khalistan supporters, who were Sikhs and indulged in terrorist activities, were killed by the Indian Army. This is why Indira Gandhi's personal Sikh body guards assassinated her.