fully amortization 和 partially amortization 的概念在哪？能解释解释吗？

问题如下：

In a securitization, time tranching provides investors with the ability to choose between:

选项：

extension and contraction risks.

senior and subordinated bond classes.

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.

考点：time tranching

解析：时间分层，可以使投资者在contraction risk和extension risk之间做选择。contraction risk是缩期风险，extension risk是延期风险。这两个风险一般是指在证券化的产品里，因为贷款的提前偿还速度和之前预设的提前还款速度不一致导致的。如果借款者可以提前还款，那么产生的是contraction risk； 如果借款者拖延还款，产生的是extension risk。故选项A正确。