问题如下：
McLaughlin and Michaela Donaldson, a junior analyst at Delphi, are now discussing how to reposition the portfolio in light of McLaughlin’s expectations about interest rates over the next 12 months. She expects interest rate volatility to be high and the yield curve to experience an increase in the 2s/10s/30s butterfly spread, with the 30-year yield remaining unchanged. Selected yields on the Treasury yield curve, and McLaughlin’s expected changes in yields over the next 12 months, are presented in Exhibit 1.
Donaldson suggests they also consider altering the portfolio’s convexity to enhance expected return given McLaughlin’s interest rate expectations.
Given McLaughlin’s interest rate expectations over the next 12 months, one way that Donaldson and McLaughlin could alter convexity to enhance expected return would be to:
选项：
A.sell call options on bonds held in the portfolio.
buy call options on long-maturity government bond futures.
sell put options on bonds they would be willing to own in the portfolio.
解释：
B is correct.
McLaughlin expects interest rate volatility to be high and the yield curve to experience an increase in the butterfly spread, with the 30-year yield remaining unchanged. To increase the portfolio’s expected return, Donaldson and McLaughlin should buy call options on long-maturity government bond futures to increase convexity.
请问这个题目为什么不是选A
我知道利率变动应该增加Convexity，但题目这里是利率上升，债券价格下降，所以Call option是不会执行的，我买个Call，价格更低，不是也能增强收益吗？
