问题如下：
Which of the following statements is most accurate about callable bonds compared to noncallable bonds?
选项：
A. They have more price volatility.
B. They have positive convexity.
C. Capital gains are capped as yields fall.
D. At low yields, reinvestment rate risk falls.
解释：
C is correct.
考点：Callable bond
解析：
Callable bonds have the following characteristics:
1) Less price volatility.
2) Negative convexity.
3) Capital gains are capped as yields fall.
4) Reinvestment rate risk increased when yields fall.
请问第四个可以怎么理解？