To determine which internal audit activity is performed in the design evaluation phase, it's essential to understand what each phase in the audit process entails. The design evaluation phase involves assessing whether the design of controls is adequate to mitigate risks to acceptable levels.

Option A: The internal auditor reviews prior audits and workpapers.

This activity typically occurs during the planning phase of an audit. Reviewing prior audits and workpapers helps the auditor understand the scope, findings, and context of previous audits, providing valuable information for planning the current audit.

Option B: The internal auditor identifies the controls over segregation of duties.

Identifying controls, particularly those related to segregation of duties, is a key part of the design evaluation phase. In this phase, the auditor assesses whether the control design, including segregation of duties, is sufficient to prevent or detect errors and fraud.

Option C: The internal auditor checks a process for completeness.

Checking a process for completeness is more aligned with the testing phase, where the auditor evaluates the operational effectiveness of controls. During this phase, the auditor ensures that all parts of a process are functioning as intended.

Option D: The internal auditor communicates the audit results to management.

Communicating audit results occurs in the reporting phase, after the audit fieldwork is complete. In this phase, the auditor summarizes findings, conclusions, and recommendations and presents them to management.