The correct answer is letter D.
Explanation: Turner is widely recognized as one of the most influential historians in the United States in the first half of the twentieth century. In 1889, he defended at Johns Hopkins University his doctoral dissertation, entitled The Character and Influence of the Indian Trade in Wisconsin, published in large form and revised in 1891. In the year 1910, he was the president of the American Historical Association. In 1933, he received the Pulitzer Prize for History for the text The Significance of Sections in American History.