Which of the following can be used in root cause analysis?

A Pareto chart ranks problems or causes by frequency or impact using the 80/20 rule to prioritize action, but it does not identify the root cause of any specific problem.

A data-flow diagram models how data moves and is transformed through a system during analysis or design, and is not used to investigate the origin of problems.

A Gantt chart is a project scheduling bar chart that displays tasks over time and is not a root cause analysis tool.

A fishbone diagram (also called an Ishikawa or cause-and-effect diagram) organizes potential causes of a problem into categorical branches - such as people, processes, equipment, and environment - allowing teams to systematically trace issues back to their root cause. It is one of the seven basic quality tools and is a primary method used in formal root cause analysis processes. Its structure is purpose-built for asking 'why does this problem occur' rather than just documenting that it exists.