Nutrition Co., a health snack company, would like to know the total impressions that have been delivered per campaign, per supply_source, per device_type. Which of the following represents how to write this query?

The correct query SELECT campaign, supplysource, devicetype, SUM(impressions) AS impressions FROM dspimpressions GROUP BY accurately aggregates impressions by the specified dimensions. The SELECT statement includes campaign, supplysource, and devicetype to show these attributes, and SUM(impressions) AS impressions calculates the total impressions. The FROM dspimpressions clause specifies the table containing the impression data. The GROUP BY clause, although incomplete in the prompt, would typically list campaign, supplysource, devicetype to ensure the sum is calculated for each unique combination of these fields. The other options are incorrect because they either misplace the SUM function, use incorrect table names, or have an incomplete GROUP BY clause that would lead to incorrect aggregation.