Security X has a higher level of systematic risk than security Z. The expected equilibrium return for X must be greater than that for Z because:

a. Z's price will fall as investors realize that Z offers lower returns.

b. if it is not, then X's price will fall and Z's price will rise as investors sell X and buy Z.

c. The Security Market Line (SML) is negatively sloped.

d. The standard deviation of X's return is greater than Z's.