To optimize a slow query involving customer names, which replacement is appropriate for enhancing execution time?

The correct choice enhances execution time by using the function NOT ISEMPTY combined with CALCULATETABLE. This approach is effective because it checks whether there are any relevant rows in the 'Order Item' table that meet specific filter conditions defined in the CALCULATETABLE function. By utilizing NOT ISEMPTY, the system quickly determines if there are any corresponding entries, allowing for more efficient data processing.

This method is particularly powerful in scenarios where filtering might significantly reduce the dataset being considered, leading to faster query performance. It ensures that any follow-up calculations can proceed only if there are meaningful rows present, avoiding unnecessary overhead.

The other options do not effectively leverage the capabilities of filtering or checking for the presence of relevant data in a manner that would enhance performance in this context. They may not adequately limit the data being processed or could lead to unnecessary computations, ultimately resulting in slower execution times.