Final answer:
The triple constraint of time, cost, and scope (including quality as a part of scope) are of equal importance unless otherwise stated, as changes to one affect the others.
Step-by-step explanation:
The most critical component of the triple constraint in project management cannot be universally singled out, as it largely depends on the specific project and its requirements. However, options A and B focus on ranking individual constraints, which is less accurate compared to the holistic perspective given in option D.
The triple constraint, which consists of time, cost, and scope - and can encompass quality as a function of scope - is a foundational concept in project management that emphasizes the interdependent nature of these factors. When managing a project, if any one of the constraints is altered, it will affect the other two.
Therefore, option D stating 'They are of equal importance unless otherwise stated' is typically correct, as each project may have its own priorities and it is the job of the project manager to balance these three constraints according to the project's specific context and objectives.