问题如下：
For a given CDO, which of the following tranches is most likely to have the highest expected return?
选项：
A.Equity.
B.Senior.
C.Mezzanine.
解释：
A is correct. The expected returns of the tranches vary according to the perceived credit risk, with the senior tranches having the highest credit quality and the junior tranches the lowest. Thus, the senior tranches have the lowest expected returns and the junior tranches have the highest. The most junior tranche is sometimes called the “equity tranche.”
B is incorrect because the senior tranches in a CDO have the lowest expected returns and the junior (or equity) tranches have the highest.
C is incorrect because the senior tranches in a CDO have the lowest expected returns and the junior (or equity) tranches have the highest. A mezzanine tranche is intermediate between the senior and junior tranches.
您好老师，
我的问题是针对讲义的，不是这道题目。
讲义最后一句话是：Holders of ABSs have effectively WRITTEN PUT OPTIONS.
这句话是如何理解的，请麻烦帮我解答一下。
