What does the subscript in h2o mean

Master planned communities outside of chicago. note: population density means people living in an area per square mile. chicago, an urban and highly populated area has a much more higher density than a desert, amish community, settlement, or nomadic region.

Answerhighlands and forests;

Wheres the answers to the question

Ithink it's d. changemodify means to change.hope it ! : )