Comprehensive and Detailed Step-by-Step Explanation:
Thoroughsystem testingbefore deployment helps identify potentialbugs, vulnerabilities, and performance issuesto prevent system failures.
* System Testing (Correct Answer - B)
* Detects defects that could lead to system crashes.
* Ensures compatibility and performance stability.
* Example:Stress testing an e-commerce application to prevent crashes on Black Friday.
* System Recovery Plan (Incorrect - A)
* Focuses on recovery after failure rather than prevention.
* Business Continuity Plan (Incorrect - C)
* Addresses overall business resilience, not application stability.
* Transaction Monitoring (Incorrect - D)
* Detects fraud and anomalies but does not prevent failures.
References:
* ISACA CISA Review Manual
* NIST 800-160 (Systems Security Engineering)

Data migration is the process of moving data from one system to another, which may involve changes in storage, database, or application. To perform a successful data migration, it is essential to understand the data structure of the new system, which defines how the data is organized, stored, and accessed. Understanding the new system's data structure will help determine the following aspects of the data migration project:
The scope and requirements of the data migration, such as what data needs to be migrated, how much data needs to be migrated, and what are the quality and performance expectations.
The data mapping and transformation rules, such as how the data elements from the source system correspond to the data elements in the target system, and what transformations or conversions are needed to ensure compatibility and consistency.
The data validation and testing methods, such as how to verify that the migrated data is accurate, complete, and functional in the new system, and how to identify and resolve any errors or issues.
Therefore, understanding the new system's data structure is a crucial first step in a data migration project, as it lays the foundation for the subsequent steps of data extraction, transformation, loading, validation, and testing.

Comprehensive and Detailed In-Depth Explanation:High employee turnover (A) poses the greatest risk because it leads to knowledge loss, operational disruptions, and potential security risks from departing employees. A constantly changing workforce can also impact compliance, training, and overall IT stability.
Other options:
* Lack of customer satisfaction surveys (B) is a business issue but not a critical IT risk.
* Aging staff (C) may be a long-term risk but does not have an immediate impact.
* Frequent software upgrades (D) can be beneficial if managed correctly.
Reference: ISACA CISA Review Manual, IT Governance and Management of IT