问题如下图：
选项：
A. 
B. 
C. 
解释：
你好，为什么A错了，support不是两种风险都降低么？谢谢
Reassign prepayment risk among tranches. Eliminate extension risk in Ptranches. B is correct. The creation of a CMO cannot eliminate or change prepayment risk; it conly stribute the various forms of this risk among fferent bonclasses. 老师你好，c是错在eliminate这个词吗，就是不能消除只能降低？
老师，请问PAC是什么？
