Which One of the Following Best Describes an Arithmetic Average

Which one of the following best describes an arithmetic average return?

A) total return divided by N - 1,where N equals the number of individual returns
B) average compound return earned per year over a multi-year period
C) total compound return divided by the number of individual returns
D) return earned in an average year over a multi-year period
E) positive square root of the average compound return