Why was trench warfare originally a good idea?

It protected the soldiers from incoming enemy fire and also gave them a place to regroup and fire safely from

answer; /// the correct answer is evidence of the olmec civilization has been found in southern american in a hot steamy forest, archaeologists have found earthen artifacts at several sites that were evidence of the olmec civilization. these   artifacts were mounds,courtyards and pyramids build of stones, also on top of the mounds were many monuments made of stone, some of these stone structures are very large, they weigh as much as 44

a because i tried to vote with just my college id and the answer was no