What Did Lehman Find Through Research into Creativity Through Analysis

What did Lehman find through research into creativity through analysis of the works of creative people and their achievements?

A) In most fields, achievement steadily decreases after age 45.
B) Scientists and mathematicians peak much later than musicians or artists.
C) People in almost every field peak at about the same age.
D) Greatness of work is not an effective or accurate measure of creativity.