Internal auditors focus on assessing the adequacy of controls to manage various risks within the organization, including operational and strategic risks. External auditors primarily focus on the accuracy and reliability of the organization's financial statements and compliance with relevant accounting standards. References:
* IIA Standard 2100: Nature of Work.
* IIA Practice Guide: Coordination and Reliance: Developing an Assurance Map.
* External Audit Standards (e.g., Generally Accepted Auditing Standards - GAAS).

According to IIA guidance, an internal audit charter should detail the responsibilities of the audit committee.
The charter is a formal document that defines the purpose, authority, and responsibility of the internal audit activity. Including the audit committee's responsibilities ensures clarity on the committee's role in overseeing the internal audit function, enhancing governance, and providing a framework for accountability and support.
The IIA Standards: Standard 1000 - Purpose, Authority, and Responsibility: "The purpose, authority, and responsibility of the internal audit activity must be formally defined in an internal audit charter, consistent with the Definition of Internal Auditing, the Code of Ethics, and the Standards." IIA Practice Guide: "Internal Audit Charter: Understanding the Components": Highlights the importance of specifying the audit committee's responsibilities in the charter.

Demonstrating due professional care involves assessing the cost of assurance in relation to the potential benefits (Option D). This approach ensures that internal audit resources are used efficiently and effectively, providing value to the organization. According to IIA Standards, Standard 1220: Due Professional Care, internal auditors must consider the extent of work needed to achieve the engagement's objectives and the relative complexity, materiality, or significance of matters to which assurance procedures are applied. Staffing audit engagements with qualified auditors (Option A), relying on prior work (Option B), and guaranteeing identification of all significant risks (Option C) do not fully encapsulate the essence of due professional care, which balances cost and benefit.
IIA Standards, Standard 1220: Due Professional Care
IIA's International Professional Practices Framework (IPPF)

Requiring management approval for expenses is an effective control to prevent inappropriate use of organizational funds and falsification of financial records. This control ensures that all expenditures are reviewed and approved by a higher authority, providing a check against potential misuse of funds. It helps in verifying the legitimacy and necessity of expenses, thereby reducing the risk of fraudulent activities by employees.
The Institute of Internal Auditors (IIA) Standards and Practice Advisories.
COSO Internal Control - Integrated Framework.
"Internal Auditing: Assurance & Advisory Services" by IIA, Chapter on Expense Management and Approval Controls.

The internal auditor should examine application controls, which directly relate to specific computer applications. These controls ensure the accuracy, completeness, and authorization of transactions processed by the system. Since the auditor's concern is whether sales staff can modify orders after shipping, which involves transactional changes in a specific application, application controls are the appropriate focus.
Information systems auditing standards and best practices.