In Comparison to Other Mortgage-Backed Securities,the Unique Characteristic of CMOs

In comparison to other mortgage-backed securities,the unique characteristic of CMOs is that:

A) CMO issuers do not retain ownership of the underlying mortgage pool
B) CMOs are issued in multiple security classes
C) The CMO mortgage pool is not overcollateralized
D) CMOs are a pay-through in which all amortization and prepayments flow through to investors