What characteristics must the input worksheet for the fit function have?

The fit function requires the input worksheet to uniquely identify records in the first column. This characteristic is crucial because the function relies on these identifiers to accurately map and link input data for analysis. Each unique identifier allows the function to understand which data points correspond to which records, facilitating proper analysis and predictions.

In this context, having a unique identifier in the first column ensures that there are no ambiguities in the dataset. When datasets contain duplicate or non-unique entries, it can lead to erroneous results, misallocation, or confusion during the fitting process, which undermines the integrity of the analysis being performed.

Other options suggest restrictions that aren't necessary for the fit function to operate effectively. For instance, limiting the data to only customer information, sales data from a specific time frame, or excluding historical data would hinder broader analysis and the applicability of the fit function across various data types and contexts. The essence lies in maintaining unique identifiers to ensure clarity and accuracy in the analysis.