Explain why much social media marketing is trial and error

 Much of social media marketing is trial and error because a certain ad may not get people's attention or might not be targeting the right people the company would want to target.

              hope this helped. >.<

Yes you are cute answer theories to explain the colonization of the new world the last great habitable landmass to be occupied by humans focus on the bering land bridge, or beringia, which emerge by siberia and alaska the last ice age.