A. natural fences built of myrrh trees have been designed to prevent the attacks, and they doHonestly when I dont see any problems in the initial sentence I panick

I dont see any problem here, we have got a good passive voice;
"and they do" says: and they do prevent.
B. natural fences have been built of myrrh trees, designed to prevent the attacks,
and they have beenHonestly, I don't see a huge problem with the modifier "designed to prevent the attacks" which in my opinion can modify "natural fences"
The problem for me is "and they have been". "They have been" what? built?
IncorrectC. natural fences built of myrrh trees are designed
for preventing the attacks,
and have"and have" still is a problem.
another problem for me is preposition "for" instead of "to"
D.
naturally built fences of myrrh trees have been designed
for preventing the attacks,
and it is"and it is" is a problem, I cant find any verb to complete it
naturally is no adverb modifying "built". Incorrect
Still "for" instead of "to"
This choice is truly antihero
E.
naturally built fences of myrrh trees
are being designed to prevent the attacks, and they do
"being" nightmare of a GMAT test taker

"naturally" is incorrectly modifying "built". it has to be adjective and modify "Fence"
Imo
Ans:
A