A、Lee Harvey Oswald. B、Jack Ruby. C、JD Tippit. D、The president’s wife. A从首段中第二句的意思直接可以得出答案，但由于文中提及人物较多，关系比较复杂，并且都是谋杀与被谋杀的关系，如果没

Lee Harvey Oswald, a 24-year-old former Marine, was being transferred from police headquarters to the county jail. The man accused of murdering the US President, John F. Kennedy, has himself been shot dead in a Dallas police station.
    The event was being covered live on television, and Americans across the country watched in astonishment as a man -- later identified as Jack Ruby, a Dallas nightclub owner -- stepped forward, drew a gun and shot Mr. Oswald at point-blank range.
    An ambulance rushed Mr. Oswald to the Parkland Hospital -- the same hospital which had fought to save President Kennedy’s life two days earlier -- but he died within minutes of his arrival.
    He was arrested about an hour after the murder, carried out as the President’s motor queue passed through the Dealey Plaza in Dallas.
    He was initially accused of the murder of a policeman, JD Tippit, who appears to have recognized him and approached him just 45 minutes after the killing of the President. Soon after, Mr. Oswald was also charged with the President’s murder.
    But, police gave no explanation of how Jack Ruby came to be in the police headquarters. The building had been under heavy guard after several calls making threats against Oswald’s life.
    Ruby came to Dallas from Chicago 10 years ago. He runs a downtown club, and is said to have links with organised criminals. Police said Ruby had told them, "1 didn’t want to be a hero -- I did it for Jacqueline Kennedy. "They said he wanted to spare the president’s wife accused of killing her husband.