When creating a display ad, Ad gallery lets you:

  • automatically create a display ad from existing ad text
  • extend a Display campaign’s reach to Google search partners
  • choose from existing design templates
  • automatically adjust image content based on campaign performance

The correct answer is:

  • choose from existing design templates

Explanation: By providing you with pre-existing design templates, it alleviates the high cost and long lead time that often comes with generating a display creative: perfect for smaller advertisers with more modest advertising budgets.

Read more here: https://support.google.com/partners/answer/2768683