D). Encourage foreigners to immigrate to the united states.
Alfred Thayer Mahan came out as one of the chief thinkers of maritime strategy and naval warfare. He focused on the naval operations that could be atrophied only by blockades and decisive battles. In the 19th century, the US established higher control on sea oriented commerce in order to conserve its economic interest by expanding its foreign markets. Thus, as per the events that occurred, he mentioned the description of his advise of pursuit of colonization, expansion of the foreign markets and developing a bigger and better navy and naval bases in his writings. Therefore, Mahan mentioned everything, except for the last option that states the encouragement of foreigners to immigrate to the United States.