Answer:
D. Better weapons and technology .
Step-by-step explanation:
The American Army always enjoyed technological superiority and superior fire power over the communist forces. The US had air and naval superiority, and also in conventional power.
But the North Vietnamese had great manpower reserves and an iron determination to fight what they saw as a foreign occupier as long as it was necessary with persistent and intrepid guerrilla tactics, an asymmetric response to a stronger adversary. History provides many examples of the Vietnamese peopleĀ“s fight against outside intruders in protracted guerrilla wars until the enemy wears down: the Chinese, the Mongols, the French and the Americans.