- Time and Day
The correct answer is: Keyword
Explanation: Content needs to be categorized before it can be associated with specific keyword and category targeting, and this can take several days after the content is published. For this reason, keyword and category targeting doesn’t work well with an inventory consisting of new or frequently changed content (for example, news and social media sites).
Read more here: https://support.google.com/displayvideo/answer/2697825