Final answer:
The bid strategy vCPM helps optimize towards viewability. Advertisers can prioritize viewability and ensure their ads are visible to users.
Step-by-step explanation:
The bid strategy vCPM, which stands for Viewable Cost Per Mille, helps optimize towards viewability. Viewability is the measure of whether an ad is actually visible to users when they visit a webpage. By setting the bid strategy to vCPM, advertisers can focus on maximizing the number of times their ads are viewed by the target audience.
With vCPM, advertisers are charged based on the number of ad impressions that meet the viewability criteria, which typically means that a certain percentage of the ad is visible on the screen for a specific amount of time. This bid strategy allows advertisers to prioritize viewability and ensure that their ads have a better chance of being seen by users.
Therefore, the correct answer is b) Viewability.