- Any mobile site or mobile app
- Mobile sites that are part of the Google Display Network
The correct answers are: youtube.com and Mobile sites that are part of the Google Display Network
Explanation: The Display Network is a collection of websites—including specific Google websites like Google Finance, Gmail, Blogger, and Youtube—that show AdWords ads. This network also includes mobile sites and apps.
Read more here: https://support.google.com/google-ads/answer/1704373