问题如下图：
选项：
A. 
B. 
C. 
D. 
解释：
为什么不是D？
NO.PZ2016070202000031问题如下 Whis the effeon the value of a callable convertible bonof a crease in interest rate volatility anstock privolatility? An increase in value e to both interest rate volatility anstoprice volatility An increase ancrease in value, respectively A crease anincrease in value, respectively A crease in value e to both A crease in stoprivolatility creases the value of the equity conversion option anthus the convertible bonprice. A crease in interest rate volatility creases the value of the interest rate call option. Because the boninvestor is short the interest rate option, this increases the value of the convertible. callable convertible bonboncall option on boncall option on stock
NO.PZ2016070202000031问题如下 Whis the effeon the value of a callable convertible bonof a crease in interest rate volatility anstock privolatility? An increase in value e to both interest rate volatility anstoprice volatility An increase ancrease in value, respectively A crease anincrease in value, respectively A crease in value e to both A crease in stoprivolatility creases the value of the equity conversion option anthus the convertible bonprice. A crease in interest rate volatility creases the value of the interest rate call option. Because the boninvestor is short the interest rate option, this increases the value of the convertible. 为什么利率波动变小，债券的call option会变便宜； 为什么股票波动变小，股票的call option会变便宜？
NO.PZ2016070202000031 Whis the effeon the value of a callable convertible bonof a crease in interest rate volatility anstoprivolatility? increase in value e to both interest rate volatility anstoprivolatility increase ancrease in value, respectively A crease anincrease in value, respectively A crease in value e to both A crease in stoprivolatility creases the value of the equity conversion option anthus the convertible bonprice. A crease in interest rate volatility creases the value of the interest rate call option. Because the boninvestor is short the interest rate option, this increases the value of the convertible. Whis the effeon the value of a callable convertible bonof a crease in interest rate volatility anstoprivolatility? Q1callable convertible bong 和converitible bon有什么区别呢。 Q2converitible bon是债转股，sigma (r) 减少，就说明这个可转债没那么有吸引力（r下降，velue上升）所以卖得贵 （答案是inrease the value)。sigma(P) 减少，说明没那么容易转成债去获得额外收益, 所以Value减少 (答案是crease the value) 老师帮忙看下理解得对吗
increase ancrease in value, respectively A crease anincrease in value, respectively A crease in value e to both A crease in stoprivolatility creases the value of the equity conversion option anthus the convertible bonprice. A crease in interest rate volatility creases the value of the interest rate call option. Because the boninvestor is short the interest rate option, this increases the value of the convertible. 利率波动下降会导致callable价值下降？为什么选b的上升呢？
Whis the effeon the value of a callable convertible bonof a crease in interest rate volatility anstoprivolatility? increase in value e to both interest rate volatility anstoprivolatility increase ancrease in value, respectively A crease anincrease in value, respectively A crease in value e to both A crease in stoprivolatility creases the value of the equity conversion option anthus the convertible bonprice. A crease in interest rate volatility creases the value of the interest rate call option. Because the boninvestor is short the interest rate option, this increases the value of the convertible. 请问call 是针对investor的，那为什么对于投资者来说，是short方呢？
