Final answer:
President Roosevelt displayed U.S. military power by sending out the Great White Fleet, which was a squadron of U.S. Navy battleships that went on a global tour as part of his 'big stick' foreign policy.
Step-by-step explanation:
The main answer to what President Roosevelt did to show U.S. military power is D. He sent out the Great White Fleet. President Theodore Roosevelt aimed to demonstrate the U.S.'s growing naval capabilities and its ability to project power globally. This was accomplished through the inception of the Great White Fleet, which was a squadron of U.S. Navy battleships that embarked on a journey around the globe from December 1907 to February 1909. This display of naval force was part of Roosevelt's 'big stick' foreign policy, which emphasized that America should engage diplomatically in international affairs while also maintaining a strong military readiness to enforce policies if necessary. The deployment of the Great White Fleet served multiple purposes, including reassuring America's allies, deterring potential adversaries, and fostering a sense of nationalism and pride in the United States' military strength.