cmo tranche 分为class ABC，面对底层资产的提前还款，谁先被提前还款？
上课老师讲的是先是A-B-C，但是在做官网题的时候，答案中说的是先c-b-a.
具体题目如下：
Q. In a declining interest rate environment, compared with a CMO’s Class A tranche, its Class C tranche will be repaid:
- earlier.
- at the same pace.
- later
Solution
A is correct. Lower interest rates entice homeowners to pay off their mortgages early because they can refinance at lower rates. The most junior tranche in a CMO will bear the first wave of prepayments until that tranche has been completely repaid its full principal investment. At that point, the next tranche will bear prepayments until that tranche has been fully repaid. Therefore, the Class C tranche of a CMO will be repaid before the more senior Class A tranche.
B is incorrect because the tranches, which have different priorities of claims on the principal payments made by the underlying mortgages, will see prepayments allocated to the most junior tranches first and the most senior tranches last.
C is incorrect because the most junior tranche in a CMO will bear the first wave of prepayments until that tranche has been completely repaid its full principal investment. At that point, the next tranche will bear prepayments until that tranche has been fully repaid. Therefore, the Class C tranche will be repaid prior to, not after, the Class A tranche.
