问题如下：
Which of the following statements about the limitation of portfolio duration is not true?
选项：
A.The measure of portfolio duration assumes a nonparallel shift in the yield curve.
B.In reality, interest rate changes frequently result in a steeper or flatter yield curve.
C.The measure of portfolio duration assumes that all rates change by the same amount in the same direction.
解释：
A is correct.
The limitation of portfolio duration is that the measure of portfolio duration implicitly assumes a parallel shift in the yield curve, which implies that 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，这道题可以详细讲一下吗？谢谢
