Answer:
coefficient of variation; Beta
Explanation:
The best measure of risk for a single asset held in isolation would be coefficient of variation which tells you the level of variation that the asset has which allows you to calculate the level of risk. The best measure for an asset held in a diversified portfolio on the other hand would be Beta. This measures the volatility of an asset/portfolio while comparing it to the market as a whole, also allowing you to calculate expected ROI.
