Which field can be used to filter to traffic events from the relevant sponsored ads campaigns?

The campaign field is the correct choice because it directly corresponds to the sponsored ads campaigns you want to analyze. In Amazon Marketing Cloud (AMC), campaign IDs are used to identify and segment data related to specific advertising initiatives. Filtering by campaign ensures you are only looking at traffic events generated by those particular campaigns. supplysource is incorrect because it identifies where the ad impression originated (e.g., Amazon.com, third-party apps) rather than the specific campaign. userid is incorrect because it identifies a unique user, which is useful for audience analysis but not for filtering by campaign performance.