Happiness Research Reveals That

Happiness research reveals that:

A) average human happiness does not change as real average per capita income grows over time.
B) within the same society, people with high incomes are happier, on average, than people with low incomes.
C) overall national happiness rises with average per capita income levels only up to about US$10,000; further rises in average real per capita GDP have little effect on happiness.
D) All of the above.
E) None of the above.