PLZ HELP ASAP Which of the following DID NOT occur as a result of RR's?
(a) The rapid growth of industry such as mining and steel.
(b) Cities grew along rail lines
(c) Southern agricultural production dropped by nearly 50%
(d) The United States was in a position to become the strongest industrial nation in the world

The constant presence of diseases or infectious agents within a given geographic area or population group. it may also refer to the usual prevalence of a given disease with such area or group. it includes holoendemic and hyperendemic diseases. a holoendemic disease is one for which a high prevalent level of infection begins early in life and affects most of the child population, leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than do children (malaria in many communities is a holoendemic disease). a hyperendemic disease is one that is constantly present at a high incidence and/or prevalence rate and affects all groups equally. so probably family history.