Final answer:
The best buffer for Roxanne's email while rejecting a customer's refund claim is option B, which positively acknowledges the customer without leading directly to the negative outcome of the refund rejection.
Step-by-step explanation:
In the context of writing a professional email to reject a customer's refund claim, the best buffer is a sentence that acknowledges the customer without suggesting a negative outcome immediately. Among the options provided, option B, 'We are glad to hear from a loyal customer.', serves as an effective buffer. This statement is neutral, acknowledges the customer positively, and does not lead immediately to the denial that will follow in the message. It helps set a courteous tone before delivering the bad news of the refund rejection.