问题如下：
Which comment regarding CDOs and covered bonds is accurate?
选项：
A.Easton’s comment
B.Avelyn’s first comment
C.Avelyn’s second comment
解释：
A is correct.
CDOs typically include some form of subordination. With subordination, a CDO has more than one bond class or tranche, including senior bond classes, mezzanine bond classes (which have credit ratings between senior and subordinated bond classes), and subordinated bond classes (often referred to as residual or equity tranches). The correlation of expected defaults on a CDO’s collateral affects the relative value between the senior and subordinated tranches of the CDO. As correlations increase, the values of the mezzanine tranches usually increase relative to the values of the senior and equity tranches.
按照新的原版书修订，这道题目的选项A是不是要改一下
