Which two elements can have their values changed by using a dashboard action?

Tableau dashboard actions can directly change Parameters and Sets, so B and C are correct. A parameter action allows a user to modify a parameter value by interacting directly with marks in a visualization. For example, selecting a mark can assign the mark's Sales value to a parameter, which can subsequently drive a calculated field, reference line, filter logic, or another analytical component. Tableau provides the dashboard action type Change Parameter specifically for this purpose. A set action similarly modifies the membership of an existing set based on interaction with marks. The action can assign selected values to the set, add values, or remove values. This enables sophisticated interactive behavior such as proportional brushing, dynamic comparisons, drill-down effects, and conditional calculations. Tableau identifies this action type as Change Set Values. Groups and bins do not have equivalent dashboard action types that dynamically modify their definitions through viewer interaction. They are data organization constructs configured during authoring. The Tableau Actions documentation explicitly lists Change Parameter and Change Set Values among supported action types. Parameter Actions documentation confirms that visualization interaction can update the target parameter, while Set Actions documentation confirms that interactions can modify values contained in a target set.