Which is the 4th riskiest asset based on the information below? [ Select] S&P 500 Small Stocks Corp Bonds World Portfolio Treasury Bills CPI Average return 2.55% 15.65% 5.35% 2.94% 0.83% -1.48% Variance: 0.10179 0.50460 0.00129 0.06968 0.00020 0.00221 Standard deviation: 31.90% 71.03% 3.59% 26.40% 1.40% 4.70%