Conversion Optimizer can help drive conversions by using conversion history and:

Conversion Optimizer can help drive conversions by using conversion history and:

  • Cost per acquisition ( CPA) goals to raise your bid when a conversion is more likely
  • Cost per click (CPC) goals to show the optimal ad when a conversion is more likely.
  • Cost per acquisition (CPA) goals to show to show the optimal ad when a conversion is more likely.
  • Cost per click (CPC) goals to raise your bid when a conversion is more likely.

Answer : Cost per acquisition ( CPA) goals to raise your bid when a conversion is more likely

Source: https://support.google.com/adwords/answer/2390684?hl=en