Cross-selling is best described as:

Cross-selling is best described as encouraging customers to buy additional products related to their original purchase. This strategy is designed to enhance the overall customer experience by suggesting items that complement their existing selection. For instance, if a customer is purchasing a camera, cross-selling might involve recommending a camera case, memory card, or tripod, which can enhance the use of the camera.

This approach not only increases the value of the sale for the business but also benefits the customer by offering them convenient options that fit their needs. It aligns perfectly with the goal of providing excellent customer service by ensuring that customers are aware of products that can enhance their original purchase, thereby helping them make more informed buying decisions.

The other options do not align with the concept of cross-selling. Offering a discount on bulk purchases relates to volume pricing strategies rather than promoting additional items. Providing a refund addresses customer satisfaction but doesn't involve suggesting additional products. Raising prices on popular items is a pricing strategy that doesn't pertain to the act of encouraging more purchases related to an existing transaction.