E. all of the above
is your answer
all of the factors on the top is true.
A) because there were lots of boot traps that finished off many American troops
B) these trails were used by the NVA, and were hard to locate
C) These inflicted heavy losses to the Allies, while having relatively less losses to their own side.
D) As mentioned before, because of unfamiliar terrain, the US couldn't put their military strength at it's strongest, as it was hard to map out and plan each attack accordingly every single time
hope this helps
