Consider a portfolio comprised of four risky securities. Assume the economy has three states with varying probabilities of occurrence. Which one of the following will guarantee that the portfolio variance will equal zero?

A. The portfolio beta must be 1.0.

B. The portfolio expected rate of return must be the same for each economic state.

C. The portfolio risk premium must equal zero.

D. There must be equal probabilities that the state of the economy will be a boom or a bust.