If IQ Tests Have Become More Sophisticated and More Culture-Fair

If IQ tests have become more sophisticated and more culture-fair, how does that help to explain the Flynn effect?

A) As people become more educated, they can handle more complicated tests.
B) As more cultures are tested, the amount of norming data available increases.
C) Earlier tests may have underestimated the intelligence of earlier generations.
D) Education programs tend to focus on the same skills as modern IQ tests.