This answer is based on the PMI Guide to Business Analysis, which is one of the reference materials for the PMI-PBA exam. According to the guide, quality is the degree to which a set of inherent characteristics fulfill requirements. Quality requirements are the criteria that define the acceptable level of performance, reliability, usability, and other attributes of the project deliverables. In a hybrid approach, which combines predictive and adaptive methods, the project manager should continually survey the quality of the deliverable to ensure that it meets the quality requirements and the stakeholder expectations. This can be done by using various quality management tools and techniques, such as inspections, audits, reviews, testing, feedback, and metrics. Continual quality surveillance helps the project manager to identify and correct any defects, errors, or deviations from the quality standards, and to prevent or mitigate any risks related to quality.