The correct answer is option 4, Bhagat Singh. Capt. Saunders, the English Police Officer, was shot dead by Bhagat Singh. Bhagat Singh was a prominent Indian freedom fighter who played a significant role in the Indian independence movement against British rule. He was a member of the Hindustan Socialist Republican Association (HSRA) and believed in armed revolution to achieve independence. In 1928, Bhagat Singh and his associates planned to explode a bomb in the Central Legislative Assembly to protest against the repressive British government. However, the bomb exploded prematurely. Later, Bhagat Singh and his partner, Batukeshwar Dutt, were arrested for being involved in the bombing incident. During the court trial, Bhagat Singh shot Capt. Saunders to avenge the death of Lala Lajpat Rai, a leading freedom fighter who had died due to injuries sustained during a protest.