According to the PMBOK® Guide (6th Edition), understanding the relationship between Process Groups and the Project Life Cycle is fundamental to project management. While they are distinct concepts, their primary similarity lies in their purpose: providing structure.

Project Life Cycle: This is the series of phases that a project passes through from its start to its completion. It provides the basic framework for managing the project, regardless of the specific work involved.

Project Management Process Groups: These are logical groupings of project management inputs, tools and techniques, and outputs (Initiating, Planning, Executing, Monitoring and Controlling, and Closing). They also provide a basic framework by defining the " how-to " of managing project activities.

Analysis of Distractors:

A (The life cycle involves three process groups): This is incorrect. There are five process groups (Initiating, Planning, Executing, Monitoring and Controlling, and Closing), and they are all applicable across the project life cycle, not just three.

C (Each project must have all processes in the five process groups): This is incorrect because of tailoring. The PMBOK® Guide emphasizes that project managers should tailor the processes; not every single one of the 49 processes is required for every project.

D (The project life cycle is managed by executing the processes): While this statement is technically a true description of how a project is run, it describes the interaction between the two concepts rather than their similarities. The question asks what they have in common (their nature as structural frameworks).