A direct response advertiser is primarily interested in generating conversions from a display campaign. To get the best return on investment, this advertiser should use:

  • Ad Scheduling
  • cost-per-day (CPD)
  • Target CPA Bidding
  • cost-per-thousand impressions (CPM) bidding

The correct answer is:

  • Target CPA Bidding

Explanation: An automated bid strategy that sets bids to help get as many conversions as possible at the target cost-per-acquisition (CPA) you set.
Note: Conversion Optimizer is now Target CPA bidding

Read more here: https://support.google.com/adwords/answer/2390684?hl=en