To help with prioritization, what is MOST important when understanding the difference between scope and quality?

In PRINCE2 Agile, it is vital to fix time and cost while allowing scope to be variable. Quality, however, is fixed. Differentiating functional requirements (what the product does) from non-functional requirements (how well it does it, e.g., performance, security) is crucial for this. Functional requirements typically represent the variable scope that can be prioritized using techniques like MoSCoW. Non-functional requirements often define the fundamental quality criteria for the solution and are therefore fixed and non-negotiable. This distinction allows teams to trade scope (functional requirements) to meet deadlines without compromising quality (non-functional requirements).

A. Combining requirements obscures the distinction between what is flexible (scope) and what is fixed (quality), making prioritization harder.
B. This is a valid technique, but the act of differentiating is the most important concept for understanding the scope/quality trade-off.
D. The order of definition is less important than the act of clearly separating them to understand what can be flexed.

AXELOS. (2015). PRINCE2 Agile® Guidance. The Stationery Office. Section 11.4.2, p. 98. ("It is important to be clear on what is a requirement and what is a quality criterion... The scope is a list of things to be delivered... quality is about the state they need to be in.")

AXELOS. (2015). PRINCE2 Agile® Guidance. The Stationery Office. Section 11.4.3, p. 99. ("Non-functional requirements are usually handled as acceptance criteria for the final product and are therefore part of the quality criteria.")