According to Researchers, Which of the Following Is the Most

According to researchers, which of the following is the most likely explanation for national differences in self-esteem scores?

A) Self-esteem is affected by genetics, and different countries have different gene pools.
B) Countries that perform well in the Summer Olympics or World Cup tend to report higher levels of self-esteem.
C) People living in different countries have different diets, and self-esteem is affected by diet.
D) People in some countries are more modest than people in other countries, so they agree with statements about self-esteem "somewhat" instead of "strongly."