Final answer:
Retailer POS data does not provide an external benchmark to gauge how retailers are doing compared to their key competitors, channel, or total market.
Step-by-step explanation:
The answer to the question is option C) External.
Retailer POS data does not provide an external benchmark to gauge how retailers are doing compared to their key competitors, channel, or total market. This means that the data from the retailer's point of sale system does not include information about other players in the industry or the overall market performance.
For example, if a retailer wants to know how they are performing compared to their competitors, they would need to look at external sources such as market research reports, industry benchmarks, or competitor data.