Risk associated with a portfolio is always less than the weighted average of risks of individual items in the portfolio due to _______                              
I.        Diversification of risks                            
II.        The fact that all accounts in a portfolio have different Beta                           
III.        The fact that risks in all the accounts in a portfolio will not materialize simultaneously

Risk associated with a portfolio is always less than the weighted average of risks of individual items in the portfolio due to diversification of risks. This means that the risk is spread out as all individual items in a portfolio will not behave in unidirectional manner or the risks in all the individual items in a portfolio will not materialize simultaneously. The market Beta of each item is also different and therefore, the market risk associated with each is also different thereby reducing the overall impact on a well diversified portfolio.