You are the project manager of a construction project. You have to close a phase of the project. Which is the only technique (or tool) available in the Close Project or Phase process?

Change control meetings are a tool used in the Perform Integrated Change Control process to evaluate and disposition change requests, not in Close Project or Phase.

The project management information system is used broadly across planning and executing processes for information storage and retrieval, but is not listed as a specific tool or technique in Close Project or Phase.

According to the PMBOK Guide, expert judgment is the key tool and technique in the Close Project or Phase process, used to assess the inputs needed to perform closure activities, validate completion criteria, and ensure all closure requirements are satisfied. It draws on specialized knowledge from individuals or groups experienced in project closure, contract administration, and organizational procedures. In earlier PMBOK editions it was listed as the sole technique for this process.

Observations are used in processes such as Collect Requirements and Manage Quality to gather data, and are not a listed tool or technique in the Close Project or Phase process.