Which of the following statements concerning risk are correct?

I. Diversifiable risk is measured by beta.

II. The risk premium increases as diversifiable risk increases.

III. Systematic risk is another name for non-diversifiable risk.

IV. Non-diversifiable risks are risks in the market that systematically impact all securities.

a. I and III only

b. I and II only

c. I, II, and III only

d. II and IV only

e. III and IV only