Final answer:
Sales revenues is considered an external performance benchmark for a product's performance in the market.
Step-by-step explanation:
The external performance benchmark for a product's performance in the market can be measured using sales revenues. Sales revenues indicate the total amount of money generated from the sales of products, which reflects the product's demand and success in the market.
On the other hand, return on sales (choice B) only measures the profitability of sales based on the cost of goods sold, and it doesn't provide a direct measure of the product's performance in the market.
Therefore, the correct answer is sales revenues (choice C).