Which Empirical Phenomenon Is Regarded as the Equity Premium Puzzle

Which empirical phenomenon is regarded as the equity premium puzzle?

A) the higher rates of return on the US stock market than those in Western Europe
B) the much higher rates of return on stocks than bonds and banks accounts
C) the greater risk aversion displayed by female investors than male investors
D) the greater proportion of bonds than stocks in Danish and Swiss portfolios
E) why some investors seek dividends while others seek capital gains