问题如下：
A main deficiency of using the weighted average of the yield durations of the individual bonds to represent a fixed income portfolio's duration is that it:
选项：
A.neglects the possible difference in the shift of different parts of a yield curve.
B.is less accurate when the yield curve is less steeply sloped.
C.is not applicable to portfolios that have bonds with embedded options.
解释：
A is correct.
The measure, calculating a bond portfolio’s duration as the weighted average of the yield durations of the individual bonds, implicitly assumes a parallel shift to the yield curve (all rates change by the same amount in the same direction). In reality, interest rate changes frequently result in a steeper or flatter yield curve.
老师，这道题可以再讲讲吗？不怎么懂，谢谢
