What action does an advertiser want customers to take if they select engagement as their campaign objective?

When an advertiser selects engagement as their campaign objective, the primary aim is to increase interactions with the content shared on social media platforms. Engagement signals include various actions users can take to interact with a post, such as liking, sharing, and commenting.

Focusing on "liking" a post is particularly effective for increasing the visibility of the content since likes can boost its algorithmic reach and show that the content resonates with users. When a post receives a significant number of likes, it’s more likely to appear in the feeds of others, potentially leading to additional engagement actions, such as comments and shares.

While sharing a post and commenting on a post are also valuable engagement actions, they generally derive from an initial interest that is often signified by a like. Visiting a website, on the other hand, typically aligns more with conversion-focused objectives rather than pure engagement, as it's seeking to direct customers to take a specific action outside of the social media platform.

Thus, the key action the advertiser encourages within the context of engagement is to like a post, making this the correct answer.