问题如下图：
选项：
A. 
B. 
C. 
解释：
c为什么不对呢？可以hedge波动率吧
NO.PZ2019122802000034 To net out the time cassociatewith options portfolios. To hee the volatility change of the unrlying assets. C is correct. The goof volatility trang strategy is to buy chevolatility ansell expensive volatility anto net out the time cassociatewith options portfolios. the goof volatility trang strategy根据原版书的原话是A和B（见下图讲义截图），和C没有关系，这个策略主要目的套利波动率这个衍生品的，而不是股票市场的。简单的大概说下就是volatility trang strategy是赚取sprea价差）——类似的the unrlying assets的两个期权，一个因为预期波动率将变高，是不是就会变贵对吧，一个因为预期波动率将变小，是不是会变便宜啊对吧。那就做多预期波动率变高的，做空波动率变小的，赚取之间的sprea同时去除不想要的因素（time cay）。 每天都鼓励你们的伯恩小哥哥 具体来说什么是net off cay
NO.PZ2019122802000034 老师您好！请问netting out time cay具体怎么操作的？按照伯恩老师说的那样，对冲掉这个time cay很简简单是做多到期日长的option做空到期日短的option，但是这样时间一长一短不还是有时间（theta因素影响）么？
NO.PZ2019122802000034 To net out the time cassociatewith options portfolios. To hee the volatility change of the unrlying assets. C is correct. The goof volatility trang strategy is to buy chevolatility ansell expensive volatility anto net out the time cassociatewith options portfolios.如果c的volatility改成price，是不是就是不能选了？
NO.PZ2019122802000034 To net out the time cassociatewith options portfolios. To hee the volatility change of the unrlying assets. C is correct. The goof volatility trang strategy is to buy chevolatility ansell expensive volatility anto net out the time cassociatewith options portfolios.這個部分我上課就有點搞不懂。他的目標我知道是 Buy chevolatility ansell expensive volatility 此外 老師上課說要 long volatility大的 然後short volatility小的 這兩句要怎麼關聯在一起 有點不太懂
To net out the time cassociatewith options portfolios. To hee the volatility change of the unrlying assets. C is correct. The goof volatility trang strategy is to buy chevolatility ansell expensive volatility anto net out the time cassociatewith options portfolios. net out就是hee的意思？对冲time cay导致的option价值下降的这个影响，具体对冲方法有没有要求掌握？没有印象了。
