What is the difference between the Sortino and the omega ratio?

a. There is no difference, they both use the accumulated variability of returns to make a judgement on portfolio efficiency.

b. Omega uses semivariance for the denominator and Sortino uses semivariance in the numerator.

c. Omega uses standard deviation of negative returns for the denominator and Sortino uses standard deviation of total returns in the denominator.

d. Omega uses a probability density function of negative returns for the denominator and Sortino uses downside deviation for the denominator.

e. Omega uses semivariance for the denominator and Sortino uses the probability density function of negative returns in the denominator.