Which tool allows for the concatenation of values for new columns?

The correct choice is the Append Fields tool, as it is specifically designed for concatenating values from different records to create new columns in your dataset. When you use this tool, it enables you to add fields from one data stream to another by appending data from one data source to the rows of the other. This leads to the creation of new columns in the output that combine the values from both sources based on the specified configuration.

The Union tool is generally used to combine datasets with the same schema, stacking rows on top of each other rather than creating new columns from concatenated values. The Cross Tab tool transforms unique values from one column into multiple columns in the output, which is different from concatenation. The Transpose tool switches columns and rows, which also does not involve creating new columns by concatenating values.

In summary, the Append Fields tool uniquely focuses on merging field values from different data streams, making it the correct answer for creating new columns through concatenation of data values.