Final answer:
The IBM Acquisition of Red Hat showed positive shareholder wealth effects for sell-offs, in contrast to the other options which were known for negative outcomes.
Step-by-step explanation:
The study showing positive shareholder wealth effects for sell-offs is d. The IBM Acquisition of Red Hat. When a large number of shareholders own a company, they benefit if the company's actions, such as sell-offs or acquisitions, create value and increase the stock price. This question refers to situations in which companies engage in major financial transactions, and the impact of those transactions on shareholder value is assessed.
In the case of IBM's acquisition of Red Hat, the action was viewed positively by the market, and it was anticipated to create a synergy that would drive future growth and innovation, thus increasing shareholder wealth. Unlike the examples given in options a, b, and c, which were associated with negative outcomes for shareholders (Johnson & Johnson faced numerous lawsuits, the Enron scandal led to the company's bankruptcy, and the AOL and Time Warner merger is considered one of the most unsuccessful mergers in history), the acquisition of Red Hat by IBM was generally seen as a strategic move by investors to boost IBM's position in the cloud computing market.