which of the statements with respect to the markowitz model is true? multiple select question. the success of a portfolio selection rule depends on the quality of the input list, that is, the estimates of expected security returns and the covariance matrix. a challenge in applying the markowitz model to portfolio optimization is that errors in the assessment or estimation of correlation coefficients can lead to nonsensical results. a challenge in applying the markowitz model to portfolio optimization is that errors in the assessment or estimation of expected returns can lead to nonsensical results. the success of a portfolio selection rule depends on the quality of the output list, that is, the estimates of expected security returns and the variance matrix.