Which of the following statements best describes Arthur M. Schlesinger Jr.'s contributions to American history?

A、He was primarily known for his role as a political advisor and his involvement in the New Deal.
B、He won the Pulitzer Prize for his work on American history, notably for his book on the presidency of Franklin
D、 Roosevelt.
C、He advocated for the isolationist policy during World War II and opposed American involvement.
D、He was a prominent civil rights activist who played a key role in the legislation of the Civil Rights Act.