Which of the following is not a stage of system development cycle?

The stage of system development cycle that is not commonly considered is "Observation". The typical stages of the system development cycle are planning, analysis, design, implementation, and testing. During the planning stage, the requirements and objectives of the system are identified. In the analysis stage, the requirements are studied in detail, and the feasibility of the system is determined. The design stage involves creating a blueprint for the system, including its architecture, interfaces, and data structures. During implementation, the system is built and the design is turned into a working system. Testing involves checking the system's performance and identifying any errors or bugs that need to be fixed. Observation is not usually considered a distinct stage in the system development cycle, but it can be seen as a part of testing or implementation. Observation involves monitoring the system after it has been implemented to ensure that it is working as intended and to identify any issues that need to be addressed.