Final answer:
An inquiry about the status of a claim is most appropriate when a reimbursement has not been received, especially if it is overdue, as in option C where the claim is 10 days old without payment.
Step-by-step explanation:
The situation in which you should inquire about the status of a claim is option C. If a claim is 10 days old and no reimbursement has been made, it's reasonable to follow up with the insurance company to ensure that the claim is being processed and to determine if there are any issues preventing payment. While the specifics can vary by insurer and policy, generally waiting over a week without any update might suggest a need to check on the claim. However, one should be aware of the insurer's typical processing times, as some might naturally take longer.
Option B is concerning because it indicates a potential issue of fraud or error, and you would need to contact the insurance company immediately to resolve the discrepancy, not just inquire about the status of the claim. And while option D, a claim being 30 days old and the Explanation of Benefits (EOB) indicating that the service was applied to the deductible, might be normal procedure, it does not typically require follow-up unless you believe there is an error with how the deductible was applied.