23. (2 points) A financial entity was able to create collateralized debt obligation (CDO) and receive a higher credit rating on parts of it than a traditional mortgage-backed security (MBS) created from the same mortgages because A. the standard deviation of returns of the tranches of the CDO were lower than the MBS. B. mortgages used to create the CDO were fundamentally less risky than those used to create the MBS. C. models used to predict default of the mortgages included in the CDO were more sophisti- cated than those used to predict default in the MBS. D. mortgage payments were prioritized in the CDO such that senior tranches were paid first in the event that some mortgages defaulted