Final answer:
The statement "The investigation of Kennedy's assassination declared that a lone assassin had killed Kennedy" is True (Option A). The Warren Commission concluded that Lee Harvey Oswald was the lone assassin who killed President Kennedy.
Step-by-step explanation:
The question refers to the investigation into President John F. Kennedy's assassination, specifically whether the investigation concluded that a lone assassin had killed Kennedy.
The investigation, known as the Warren Commission, was established by Kennedy's successor, President Lyndon Johnson, and led by Supreme Court Chief Justice Earl Warren.
The Commission's report, released in 1964, concluded that Lee Harvey Oswald acted alone in assassinating President Kennedy.
Despite the Warren Commission's findings, many Americans remained unconvinced, leading to various conspiracy theories about the assassination.
Nonetheless, no credible evidence has been presented to disprove the Commission's conclusion that Oswald was the lone assassin.
Thus, the answer to the question is True (Option A).