Which of the Following Is the Best Definition for the Concept

Which of the following is the best definition for the concept of arithmetic average return?

A) The return earned in an average year over a multi-year period.
B) The hypothesis is that actual capital markets are efficient.
C) The average squared deviation between the actual return and the average return.
D) Statistical measure of maximum loss used by banks and other financial institutions to manage risk exposures.
E) The positive square root of the variance.