- Frequency cap
- Keyword targeting
- Dynamic targeting keys
- Priority
The correct answer is: Priority
Explanation: Priority: This determines which ad serves when a user is eligible for multiple ads on the same placement. Priority is set by default based on ad type and schedule. The lower the priority number, the greater the priority with which it is served.
Read more here: https://support.google.com/campaignmanager/answer/2826012