Calculating portfolio duration as the weighted average of time to receipt of the aggregate cash flows:
A. accommodates portfolios that include callable bonds.
B. facilitates the evaluation of the effect of benchmark yield changes on portfolio value.
C. results in a theoretically correct but less commonly used measure of portfolio interest rate risk.
解析：选C。通常久期的计算是单个债券久期的加权平均值，题干中的做法不常用，但理论上正确。A项，为*现金流确定性，不能包括嵌入期权或FRN。B项，现金流收益率的变化可能与基准收益率不同，所以”有助于“的说法不正确。
Which ... relating to yield volatility is most accurate? If the term structure of yield volatility is downward sloping, then:
A. short-term rates are higher than long-term rates.
B. long-term yields are more stable than short-term yields.
C. short-term bonds will always experience greater price fluctuation than long-term bonds.
解析：选B。题干设定收益率波动(yield volatility)的期限结构向下倾斜，因此短期收益率波动高于长期收益率波动，即长期收益率较为稳定。A项说的是 rates，C项说的是 price，和 yield 不能等同。
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