How did the US military move troops quickly across the jungle during the Vietnam War? in bombers in helicopters in supply lines in quick marches

In helicopters so choice B

Not only the jungle was a major obstacle for the mobility of troops in Vietnam, but also its mountainous terrain. Before the involvement of the U. S. in Vietnam, a high ranking officer dubbed Vietnam "a nightmare terrain for maneuvers." In anticipation to the participation of U. S. troops in the conflict between South and North Vietnam, the U. S. Army ordered the test of helicopters as an alternative to wheeled-vehicles for the transport of troops, weapons, ammunition, supplies and wounded personnel and casualties. The unit designated for the study of the effective use of the helicopter was the 1st Division of Cavalry, which had served in World War II equipped with tanks instead of horses. Once the tactics of "air mobility" were tested and proved, the division received the name of "1st Air Cav", and all of its units became famous in Vietnam as merely "Air Cav."

After the Air Cav division demonstrated the efficiency of air mobility supported by helicopters, other units in the army were trained in their use as well as some units of the Marine Corps.