The main difference between MacArthur's and Truman's strategies in Korea was that: Truman favored a policy of neutrality, while MacArthur supported containment.
Truman supported containment, while MacArthur wanted to use nuclear weapons against the Soviets.
MacArthur thought the U. S. should take control of Korea, while Truman thought the U. S. should hand over control to the Soviets.
None of these choices are correct.

Truman supported containment, while MacArthur wanted to use nuclear weapons against the Soviets.

Explanation:

The main difference between MacArthur's and Truman's strategies in Korea was that "Truman supported containment, while MacArthur wanted to use nuclear weapons against the Soviets."

Truman believed that it will be more effective for the United States to use the policy of containment such that instead of going full-blown war against the Soviet Union, the war will be fought in such a way that it will not be direct but still be effective to contain the spread of communism.

On the other hand, MacArthur believed that the United States should be more aggressive and fight the Soviet Union with nuclear weapons and direct-fire combat.