问

问题如下：

The CDO tranche with a credit rating status between senior and subordinated bond classes is called the:

选项：

A.

equity tranche.

B.

residual tranche.

C.

mezzanine tranche.

解释：

C is correct. The mezzanine tranche consists of bond classes with credit ratings between senior and subordinated bond classes.

A is incorrect because the equity tranche falls within and carries the credit rating applicable to the subordinated bond classes.

B is incorrect because the residual tranche falls within and carries the credit ratings applicable to the subordinated bond classes.

考点：CDO tranche

解析：A、B选项都是次级层级的意思，在分层结构中处于最后一层，收到的是剩余现金流。而C选项处于senior和subordinated层级之间，故正确。