Introduction:
The Corporate Governance Combined Code of Practice is a set of principles and guidelines designed to promote good corporate governance in the UK. It provides a framework for companies to follow in order to ensure accountability, transparency, and ethical behavior.

Explanation:
The correct answer is option 'A' - Acceptability. Acceptability is not one of the underlying principles of the Corporate Governance Combined Code of Practice. The code is primarily focused on principles such as integrity, openness, and accountability, which are essential for effective corporate governance.

Integrity:
- Integrity is one of the fundamental principles of corporate governance.
- It refers to the commitment of individuals within the organization to act with honesty, transparency, and ethical behavior.
- Companies are expected to have a strong ethical culture and to promote integrity throughout their operations.

Openness:
- Openness is another important principle of corporate governance.
- It emphasizes the importance of transparency and information sharing within the organization.
- Companies are encouraged to provide timely and accurate information to shareholders, employees, and other stakeholders.

Accountability:
- Accountability is a key principle of corporate governance.
- It refers to the responsibility of individuals and organizations to answer for their actions and decisions.
- Companies are expected to have effective systems in place to ensure accountability, including clear lines of responsibility and mechanisms for monitoring and reporting performance.

Conclusion:
In conclusion, the underlying principles of the Corporate Governance Combined Code of Practice include integrity, openness, and accountability. Acceptability is not one of the principles emphasized by the code. Following these principles can help companies establish good corporate governance practices and maintain the trust and confidence of stakeholders.