(A) ROAS, ACOS
(B) Impressions, ACOS
(C) ACOS, impressions
(D) ACOS, ROAS
If the main target for your campaign is sales efficiency then you need to measure this using ACOS. ACOS means the % of total sales you spend on advertising so a lower ACOS value is better. If you are targeting brand awareness then you can measure this using impressions because people will know more about your brand if your ad appears in front of as many customers as possible.
This question is a part of the Amazon Sponsored Ads Foundations Certification Assessment. You can find answers to all the questions asked in this exam in our Amazon Sponsored Ads Foundations Certification Assessment Answers page.