A carrier must take one of the following actions within 45 days of the receipt of a hospital bill, but it cannot __________ the claim.

The requirement that a carrier must take action within 45 days of receiving a hospital bill is crucial for ensuring timely processing of claims and facilitating healthcare services for patients. The term "hold" implies that the carrier would simply delay the processing of the claim without any resolution. This is not permissible under the regulations governing insurance claims, as it could lead to unnecessary waiting periods for healthcare providers and individuals seeking reimbursement or payment for services rendered.

On the other hand, options like denying, disallowing, or paying the claim represent definitive actions that the carrier is required to take. Denying or disallowing requires the carrier to provide a justification for the rejection of a claim, often accompanied by specific reasons or codes. Paying implies that the claim has been approved and the carrier will issue payment, thus fulfilling their obligation. Therefore, the inability to merely hold the claim without action underscores the necessity for carriers to actively manage and resolve claims within a specified timeframe to promote efficiency and accountability within the health insurance system.