A is the most reasonable answer, Presidents Eisenhower and Carter were not president during the US involvement in Vietnam and Nixon's Vietnam plan stated for an increase in troops to the country.
The correct option is "President Nixon announced a Vietnamization plan for withdrawal of U.S. troops.
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President Nixon outlined a plan called Vietnamization, which consisted of a process to withdraw US troops from Vietnam, while fighting was returning to the Vietnamese in the south. The withdrawal of US troops began in July 1969.
The five-year plans do not certainly justify the tremendous cost borne by the soviet people. This is because the plan only brought glory to Stalin but did not improve the welfare of the people as is reflected in the economic gap between the Soviets and other western democracies
