Final answer:
The statement that has been found to be true is option d: All of these. Firms that emphasize ethics outperform firms that don't, corporations that mention ethics have lower performance, and companies with a strong code of ethics face challenges in competing over the long run.
Step-by-step explanation:
The statement that has been found to be true is option d. All of these. Firms that emphasize ethics have been found to outperform firms that don't emphasize ethics. Additionally, corporations that mention ethics in their management reports have been found to have lower than average performance. And companies with a strong code of ethics and sense of integrity and honor may face challenges in competing over the long run. These findings highlight the importance of ethics in business and how it can impact performance and competitiveness.