The Preston curve describes the relationship between per capita income and life expectancy (LE) as an indicator of population health. It shows that A) increased national income increases life expectancy linearly. O B) increases in LE fall to negatives upon a country reaching per capita upper middle income. (C) increases in LE speed up upon a country reaching per capita upper middle. (D) increases in LE slow down upon a country reaching per capita upper middle income. (E) increases in LE slow down upon a country leaving absolute poverty