问题如下：
Which of followings is not one of the limitations of equity index derivatives over cash-based portfolio?
选项：
A. A
suitable exchange-traded futures contract may not be available
B. Derivatives
usage is maybe restricted by regulatory bodies
C. portfolio
exposures can be tactically adjusted quickly and at a low cost.
解释：
C is correct.
考点：Derivatives-Based Approaches
解析: 许多衍生品合约的流动性很高，有时甚至超过了基础资产现金。因此在这种情况下，投资组合的风险敞口可以迅速地以低成本进行战术调整。选项C是股指衍生产品的优点而非限制。
这道题题干是啥意思？根据老师对其他问题的回答，题干有这个意思--“相比现金直接买股票，买股票指数的衍生品”，没看出来啊…cash-based portfolio是啥意思？咋理解为现金直接买股票呀?
