Answer: the correct answer is C. He was an isolationist
Explanation: Alfred Thayer Mahan (September 27, 1840 – December 1, 1914) was a United States naval officer and historian, whom John Keegan called "the most important American strategist of the nineteenth century. His book The Influence of Sea Power Upon History, 1660–1783 (1890) won immediate recognition, especially in Europe, and with its successor, The Influence of Sea Power Upon the French Revolution and Empire, 1793–1812 (1892), made him world-famous and maybe the most influential American author of the nineteenth century. Mahan was not an isolationist, on the contrary, he supported commerce with other nations and he wrote about the importance of having a strategic naval power.