Final answer:
The president is using the National defense argument to justify trade restrictions on imported ball bearings, concerned with national security and self-reliance during wartime. The option (D) is correct.
Step-by-step explanation:
The president is using the national defense argument to justify the trade restriction on ball bearings. He argues that imposing a tariff on ball bearings is necessary because they are a necessary input into the production of various weapons.
The president believes that free trade would make the United States overly dependent on foreign countries for the supply of ball bearings, making it vulnerable in case of war when sufficient ball bearings may not be available to make weapons for defense. Therefore, option (D) is correct.