Which one of the following includes four stages called Plan, Do, Check and Act?

The Deming Cycle (also called the PDCA cycle) is explicitly defined by its four sequential stages - Plan, Do, Check, and Act. It was developed by W. Edwards Deming as a method for iterative process improvement and is directly referenced in ITIL as the basis for continual service improvement.

The continual service improvement approach in ITIL uses a seven-step model ('What is the vision?' through 'How do we keep the momentum going?'), not the four PDCA stages.

The seven-step improvement process is a distinct ITIL CSI process with seven defined steps for gathering and processing improvement data, not a four-stage cycle.

The service lifecycle is the overarching ITIL framework with five stages (Service Strategy, Service Design, Service Transition, Service Operation, Continual Service Improvement), not a four-stage PDCA model.