The purpose of a follow-up audit is to verify the completion and effectiveness of corrective actions taken by the auditee in response to the nonconformities identified in a previous audit1. A follow-up audit is a type of audit that is conducted after an initial audit, and it focuses on the specific areas where nonconformities were found and corrective actions were agreed upon2. A follow-up audit can be conducted as a separate audit or as part of a scheduled audit, depending on the nature and severity of the nonconformities and the audit programme objectives3.
The other options are not the purpose of a follow-up audit, but rather the purpose of other types of audits. For example:
* Option A is the purpose of a performance audit, which is a type of audit that evaluates the effectiveness of the management system in achieving its intended results4.
* Option B is the purpose of a compliance audit, which is a type of audit that verifies the conformity of the management system with the specified requirements, such as the ISMS objectives5.
* Option C is the purpose of a process audit, which is a type of audit that examines the inputs, activities, outputs, and interactions of a specific process within the management system, such as the risk treatment process.

Comprehensive and Detailed In-Depth
B . Correct Answer:
The Stage 1 audit (preliminary assessment) focuses on understanding the organization and its processes, identifying key areas for in-depth auditing in Stage 2.
Materiality-based prioritization occurs in Stage 1 to ensure the Stage 2 audit focuses on critical areas.
A . Incorrect:
Initial contact is only for scheduling and preliminary discussions.
C . Incorrect:
By Stage 2, the key areas should already be identified and the focus is on detailed auditing.
Relevant Standard Reference:

According to the PECB Candidate Handbook for ISO/IEC 27001 Lead Auditor, a correction is an action to eliminate a detected nonconformity, such as rework, repair, or replacement1. The examples of A, B, C, and E are corrections because they fix the errors or defects that caused the nonconformities, such as a missing signature, a missing guide, a wrong date, or a wrong colour code. The other examples (D, F, G, and H) are not corrections, but corrective actions, because they address the root causes of the nonconformities, such as inadequate training, poor planning, ineffective documentation, or unclear responsibility2. References: 1:
PECB Candidate Handbook for ISO/IEC 27001 Lead Auditor, page 35, section 4.5.12: PECB Candidate Handbook for ISO/IEC 27001 Lead Auditor, page 36, section 4.5.2.

Materiality should be considered during the initial contact to obtain reasonable assurance that the audit can be successfully completed. Determining materiality helps establish the threshold for the significance of audit findings, ensuring that the audit focuses on substantial issues that could impact the audit conclusions.
References: ISO 19011:2018, Guidelines for auditing management systems