The last Americans to leave South Vietnam were evacuated by from the U. S. embassy.
o helicopter
o
boat
O train
O plane

Helicopter.

Explanation:

The fall of Saigon heralds the end of American military presence in the Vietnamese nation. This event is also regarded as the Liberation of Saigon, with the People's Army of Vietnam (PAVN) and the Viet Cong overtaking the power in the nation which led to the evacuation of the American people from Vietnam.

The evacuation of American citizens and "at-risk" Vietnamese from Saigon was code-named "Operation Frequent Wind". This operation oversaw the evacuation of the people from the United States' embassy by helicopter. The last Americans were flown away from the country by helicopter. John Valdez was one of the last to board the helicopter that took them away from the nation on April 30, 1975.

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explanation:

you didn't give us the poem, or the title of the poem. but it is essential for you to give us that, otherwise we can not detect when the poem has a tonal shift!