An advertiser can use a remarketing tag to target people who’ve:

A) searched on YouTube for videos about products like hers
B) set up multiple YouTube accounts
C) posted videos on YouTube that mention her products
D) subscribed to or unsubscribed from her YouTube channel

The correct answer is:

D) subscribed to or unsubscribed from her YouTube channel

Explanation: Remarketing lists are created by first linking your YouTube account to your AdWords account. Once you link accounts, you can create remarketing lists that reach people who have done the following YouTube-related actions:

  • Viewed any video from a channel
  • Viewed any video (as an ad) from a channel
  • Liked any video from a channel
  • Commented on any video from a channel
  • Subscribed to a channel
  • Added any video from a channel to a playlist

Read more here: https://support.google.com/partners/answer/2545661