为什么波动率越大，knock-out option越不值钱啊？不是说波动和期权价格是正相关吗？

问题如下：

Looking at a risk report. Mr. Woo finds that the options book of Ms. Yu has only long positions and yet has a negative delta. He asks you to explain how that is possible. What is a possible explanation?

选项：

The book has a long position in up-and-in call options.

The book has a long position in binary options.

The book has a long position in up-and-out call options.

The book has a long position in down-and-out call options.

解释：

As the underlying assets’ price increases the up-and-out call options become more vulnerable since they will cease to exist when the barrier is reached. Hence their price decreases. This is negative delta.