Which of the following best explains the term burn-out factor? Select one: O A. The required interest spread of a pass-through security over a treasury when prepayment risk is taken into account. O B. The aggregate percent of the mortgage pool that has been prepaid prior to the month under consideration. O C.A mortgage-backed bond issued in multiple classes or tranches. O D. The percent of mortgage contract that is transferred from the seller to the buyer of a house. O E. Bonds collateralized by a pool of assets