NO.PZ2019012201000021
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。
请问这里的cash-based portfolio具体是指什么？
为什么说衍生品合约的流动性会超过现金？
