问题如下：
The portfolio strategy implemented by McLaughlin last year is mostly likely to be described as:
选项：
A. a carry trade.
B. a barbell structure.
C. riding the yield curve.
解释：
C is correct.
Last year, McLaughlin expected the yield curve to be stable over the year. Riding the yield curve is a strategy based on the premise that, as a bond ages, it will decline in yield if the yield curve is upward sloping. This is known as "roll down"; that is, the bond rolls down the (static) curve. Riding the yield curve differs from buy and hold in that the manager is expecting to add to returns by selling the security at a lower yield at the horizon. This strategy may be particularly effective if the portfolio manager targets portions of the yield curve that are relatively steep and where price appreciation resulting from the bond’s migration to maturity can be significant. McLaughlin elected to position her portfolio solely in 20-year Treasury bonds, which reflect the steepest part of the yield curve, with the expectation of selling the bonds in one year.
老师，请问carry trade 中的intra-market为什么有interest rate risk？我知道是长期利率减去短期利率，但假设不是stable yield curve 吗？收益率不变呀，为什么会有interest rate risk?
