Final answer:
The correct configuration option used to output the data is Exclude Nulls.
Step-by-step explanation:
The correct answer is Exclude Nulls because this configuration option excludes any null values from the combined output. When using the union tool, two or more inputs are combined by stacking them vertically or horizontally. By selecting the Exclude Nulls option, the resulting output will only include non-null values, filtering out any null values from the original inputs.