D. 1969 ( The united States announces a plan to begin withdrawing U.S troops from Vietnam.
Explanation:
Vietnamization was a war policy that was initiated and adopted by President Nixon in Vietnam in 1969 by the U.S to start withdrawing their troops from Vietnam. The withdrawal was necessitated as result of increase reliance in the S.Vietnam Army which lead to U.S withdrawing up to 540,000 of his army from South Vietnam.
However, it must be noted that the withdrawal lead to the South Vietnam taking responsibilities in the fighting the war but the American's made support with cash, weapon and military advice.
