What Was the Flaw in American Officials' Assumption That the U.S.military's

What was the flaw in American officials' assumption that the U.S.military's superior technology and power would defeat the Communist forces in South Vietnam?

A) Their advanced weapons were ill suited to the guerrilla warfare practiced by those forces.
B) The Communist forces actually had military technology equal to that of the U.S.military.
C) American military commanders did not yet understand their own technology.
D) The fighting took place in urban areas of South Vietnam and made the technology useless.