Which of the following statements is most correct?

a. Diversifiable risk refers to risk arising from macro factors such as Feds monetary policy

b. In a fully diversified portfolio of stocks, only market risk remains

c. A stocks standard deviation measure its diversifiable risk

d. An uncertain event is the same as a risky event in finance, even if it is not measurable

e. A stock portfolio has less risk than a single stock because stocks tend to move together, thus less volatility