Which approach is important for ensuring transparency in programmatic advertising?

Using a whitelist is an important approach for ensuring transparency in programmatic advertising because it allows advertisers to specify and control which publishers and inventory sources their ads will be displayed on. By creating a whitelist, advertisers gain visibility and confidence in where their ads appear, helping to mitigate concerns about ad placements on disreputable or irrelevant sites. This not only enhances brand safety but also fosters stronger relationships with trusted media partners, ensuring that advertising budgets are spent effectively.

In contrast, the other options do not directly contribute to transparency. Implementing ad blockers restricts ad visibility and can limit the reach of advertising campaigns, while reducing ad frequency may improve user experience but does not provide clarity regarding where and how ads are shown. Increasing ad visibility pertains to making ads more noticeable, which could lead to more user engagement but does not ensure that ads are placed in trustworthy environments. Therefore, using a whitelist directly addresses the need for transparency and accountability in the programmatic advertising ecosystem.