Which of the following is considered a containment tactic?

Diking is considered a containment tactic because it involves creating a barrier or embankment to prevent hazardous materials from spreading. This practice is essential in managing spills, as it helps confine the material to a specific area, minimizing environmental contamination and allowing for more effective cleanup.

Pooling, while it refers to the accumulation of liquids, does not actively create a barrier and could lead to spreading rather than containment. Retention typically involves capturing fluids, which is important for managing the hazard but does not serve the same proactive containment purpose as diking. Stabilization focuses on making a hazardous situation safe, rather than containing the spill itself. Therefore, diking stands out as a dedicated technique for confining hazards, making it the correct answer.