Which statements on risks are true? (3 good answers) Select one or more: a. In a portfolio composed of more than 30 stocks, the specific risk is close to zero. b. According to the CAPM model (Capital Asset Pricing Model), the expected return of a stock increases with its total risk. c. Risk means uncertainty. It could lead to positive results for investors in some cases, and it could also lead to negative results in other cases. d. The risk of a stock is usually measured by the standard deviation of the annual return of the stock. e. Portfolio diversification is capable of reducing the systematic risk