If you choose a target cost-per-acquisition (CPA) of US$15, AdWords will automatically adjust your bids to try to get as many conversions at what amount, on average?
The correct answer is:
Target CPA automatically sets Search or Display bids to help get as many conversions as possible at the target cost-per-acquisition (CPA) you set. Some conversions may cost more or less than your target. AdWords automatically adjusts bids but doesn’t exceed your bid on average.
Target CPA is an AdWords Smart Bidding strategy that sets bids to help get as many conversions as possible at the target cost-per-acquisition (CPA) you set.
Read more here: https://support.google.com/adwords/answer/6268632?hl=en