An advertiser made edits to an AdWords ad and noticed that the position of the ad decreased. What is the most likely cause for the decrease in position?

An advertiser made edits to an AdWords ad and noticed that the position of the ad decreased. What is the most likely cause for the decrease in position?

  A)  The Quality Score for the account was reset after the ad was edited
  B)  The advertisers landing page is down for maintenance
  C)  The edited ad is less relevant to the keywords within the ad group
  D)  The edited ad has a lower conversion rate after the changes were made