Which of the following is NOT one of the three key numbers in Google Analytics for improving content?

B. Traffic Sources is the correct answer because it is not one of the three key metrics typically used to improve content performance in Google Analytics. The three key numbers often emphasized for content improvement are Average Time on Page, which indicates how long users are engaging with content; Referrals, which show where users are coming from to access the content; and Interests, which help in understanding the demographics and preferences of the audience engaging with the content.

Traffic Sources, while still an important aspect of overall website performance and user acquisition, does not directly measure content engagement or its effectiveness in the same way the other metrics do. Understanding where traffic originates can inform marketing strategies, but it does not indicate how well the content itself is performing or how it can be improved. In contrast, the other three metrics provide direct insights into user interaction and behavior, making them crucial for refining and enhancing content strategies.