What does a Flip-over Poison Pill enable shareholders to do?

The correct answer highlights the unique mechanism of a Flip-over Poison Pill, which allows shareholders of the target company to buy shares of the acquiring company at a discounted price after a merger attempt. This defensive strategy is designed to make a hostile takeover more expensive and less attractive for the aggressor by diluting their equity value.

In practice, should an acquirer attempt to take over the target company, the existing shareholders of the target are given the right to convert their shares into shares of the acquirer's stock at the discounted rate stipulated in the plan. This can effectively diminish the financial appeal of the bid, as it enables shareholders of the target company to benefit from the acquisition rather than being sidelined in the process. As a result, the Flip-over Poison Pill serves to protect the interests of the target company's shareholders by preventing unwanted takeovers and making such attempts costlier for the acquirer.

The other choices do not accurately reflect the nature of a Flip-over Poison Pill: purchasing additional shares from the company at a discount or accessing special dividend rights are not relevant actions facilitated by this specific defense mechanism, nor does it involve trading shares in a future acquisition.