NO.PZ2016031001000097
问题如下：
In a securitization, time tranching provides investors with the ability to choose between:
选项：
A.extension and contraction risks.
B.senior and subordinated bond classes.
C.fully amortizing and partially amortizing loans.
解释：
A is correct.
Time tranching is the process in which a set of bond classes or tranches is created that allow investors a choice in the type of prepayment risk, extension or contraction, that they prefer to bear. Senior and subordinated bond classes are used in credit tranching. Credit tranching structures allow investors to choose the amount of credit risk that they prefer to bear. Fully and partially amortizing loans are two types of amortizing loans.
如何理解这道题A选项的extension和contraction
