The ISTOB glossary defines Quality Assurance as: "Pail or quality management focused on providing confidence...

Quality Assurance (QA) activities are focused on providing confidence that quality requirements will be fulfilled through planned and systematic processes. These activities are preventive in nature, aimed at ensuring quality is built into the product from the beginning.

Requirements elicitation (A) is part of the requirements engineering process and is concerned with gathering the needs and conditions to meet for a new or altered product.

Defect analysis (B) can be part of QA activities as it involves analyzing defects to prevent them in future development cycles.

Functional Testing (C) and Performance Testing (D) are types of dynamic testing, which are actually Quality Control activities rather than Quality Assurance. They are concerned with the identification of defects in the product, not with the processes to prevent defects.

Since the question asks for an activity that is NOT part of Quality Assurance, options A and B are incorrect because they can be part of QA activities. Between C and D, while both are dynamic testing activities, Functional Testing (C) is more directly related to verifying the functionality against specified requirements, which is more aligned with Quality Control. Therefore, C is the best answer.