问题如下：
The junior and senior tranches of an asset- backed security:
选项：
A.have equivalent expected returns.
B.have claims on separate underlying portfolios.
C.may be differentially impacted by prepayments or credit losses.
解释：
C is correct. An asset- backed security is a derivative contract in which a portfolio of debt instruments is assembled and claims are issued on the portfolio in the form of tranches, which have different priorities of claims on the payments made by the debt securities such that prepayments or credit losses are allocated to the most junior tranches first and the most senior tranches last.
A is incorrect because the expected returns of the tranches vary according to the perceived credit risk, with the senior tranches having the highest credit quality and the junior tranches the lowest. Thus, the senior tranches have the lowest expected returns and the junior tranches have the highest. Notably, in a bond mutual fund or an ETF, all investors in the fund have equal claims, and so the rate of return earned by each investor is the same.
B is incorrect because an asset- backed security is a derivative contract in which a single portfolio of securities is assembled and claims are issued on the portfolio in the form of tranches.
请问老师b选项是什么意思？
