On the Average, People Without Much Wealth Rate Themselves Almost

On the average, people without much wealth rate themselves almost as happy as very wealthy people do. However, it is difficult to draw any conclusion from these results because

A) people in the least wealthy countries rate themselves much happier than people in the wealthiest countries.
B) the results probably reflect the influence of the principle of isomorphic incongruity.
C) happiness ratings fluctuate enormously from one week to another for most people.
D) we cannot be sure that a certain number on a rating scale means the same thing to different people.