Which tool is used to discover and examine connections between items in a complex system?

The tool that is used to discover and examine connections between items in a complex system is Link Analysis. This method focuses on exploring and visualizing the relationships and interactions between different entities or data points. Link Analysis is particularly useful in various fields including social network analysis, fraud detection, and organizational behavior, where understanding the relationships and dependencies between items can provide valuable insights.

By utilizing Link Analysis, analysts can uncover patterns, identify key influencers, and better understand the structure of a network or system. This capability is essential in situations where the connections between items are complex and not immediately obvious.

On the other hand, the other options serve different purposes: Sector Analysis typically focuses on evaluating specific segments of a market or dataset; Data Analysis is a broader term referring to the process of inspecting, cleansing, and modeling data to discover useful information; and Trend Analysis is concerned with identifying patterns or trends over time rather than specific connections between items. Thus, Link Analysis uniquely addresses the need to explore and understand the connections within a complex system.