问题如下图：
选项：
A. 
B. 
C. 
D. 
解释：
Grace_M_Han · 2017年10月19日
Not sure if Im correct but based on work experience, vol can be normal or lognormal too. Before 2012, industry practice was to use lognormal vol. After some contries adopted negative interest rate policy, banks/security firms started using normal vol to account for negative interest rate scenario. ATM vol will differ the most.