If your ad serving option is set to "optimize" and there are multiple variations of your text ads within the same ad group, AdWords will:

77) If your ad serving option is set to "optimize" and there are multiple variations of your text ads within the same ad group, AdWords will:

  A)  automatically try to show the best performing ad more often
  B)  automatically increase your quality score based on the average CTR of the ad group
  C)  automatically serve the ad with the highest maximum CPC the most often

  D)  automatically lower your bids according to your CPA goal