"the low level of immigration between 1930 and 1945 is most directly related to
(1)passage of the chinese exclusion act
(2)the great depression and world war ii
(3)the cold war and the civil rights movement
(4)improvements in living standards in europe and asia"

The level of immigration between 1930 and 1945 is most directly related to the Great Depression and World War ll. Due to the poor economy with little opportunity for better living standards, very few people were willing to immigrate to the USA.

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.