One can use the equations of the Markowitz model to derive the CAPM equation. At this point, one would be wrong to conclude that this is the CAPM model. What additional argument is necessary to make the transition from one model to the other?

a. All other options are necessary.

b. There is a single investor who holds the mean-variance efficient portfolio.

c. There is at least one investor who holds the market portfolio.

d. Investors know the returns and standard deviations of all securities in the economy.