A GIS analyst is trying to conduct overlay analysis using the Union tool but is...

In ArcGIS Pro, ared Xnext to a parameter in a geoprocessing tool typically indicates an invalid input due to conflicts with the current environment settings. One of the most common causes is when theProcessing Extentenvironment setting is configured in a way thatexcludesthe actual input features.

TheUniontool requires that input features fall within the set extent. If the Processing Extent does not cover any part of one or more input features, they are considered invalid and flagged with a red X, preventing the tool from running.

The software checks whether all input features are accessible within the defined extent. If they are not, this pre-validation error is triggered—even if the inputs are valid in terms of geometry or feature type.

Option A is incorrect because geometrical intersection is not a requirement for Union to run—it simply overlays features and includes all areas.

Option C is also incorrect, as the Union tool does indeed require polygon feature classes, but if incorrect feature types are used, a different error (not a red X related to extent) is shown.

This confirms that the red X in this scenario is caused by the Processing Extent settings not including the input features, making the correct answer B.