XO A collateralized mortgage obligation (CMO) I. is a security backed by a pool of mortgages. II. distributes all interest and principal payments to all tranche holders on a pro rata basis III. reduces the uncertainty concerning the maturity of a mortgage backed security. IV. provides a risk/return pattern not available with typical mortgage pass through securities. Select one: a. I and III b. I, II, III c. II, III, IV d. I, III, IV Oe. All of them