How are user inputs FIRST gathered in the 'quality' practice?

In PRINCE2 Agile, quality is primarily about meeting customer requirements and acceptance criteria. The initial inputs from users are captured as requirements, which are commonly expressed as user stories. These user stories, along with their associated acceptance criteria, are collected and prioritized in the product backlog. This forms the foundation of the quality practice, as delivering what is described in these stories to the agreed-upon standard (Definition of Done) is the measure of quality.

B. Epics are large, high-level user stories. While they are an input, the more granular user stories are the primary initial gathering format.
C. The Definition of Done is a quality standard applied to user stories; it is not the initial gathering of user requirements themselves.
D. A quality control activity is a check performed on a finished product or deliverable, not the initial gathering of user inputs.

AXELOS. (2018). PRINCE2 Agile® Foundation. TSO (The Stationery Office). Section 8.1, p. 65.

AXELOS. (2018). PRINCE2 Agile® Foundation. TSO (The Stationery Office). Section 13.2, p. 106.