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

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。