Investment a Has an Expected Return of 15% Per Year,while

Investment A has an expected return of 15% per year,while investment B has an expected return of 12% per year.A rational investor will choose

A) investment A because of the higher expected return.
B) investment B because a lower return means lower risk.
C) investment A if A and B are of equal risk.
D) investment A only if the standard deviation of returns for A is higher than the standard deviation of returns for B.