The correct answer is Participation or contribution rules have been violated . Under the Health Insurance Portability and Accountability Act (HIPAA), group health insurance plans are generally subject to guaranteed renewability requirements . This means that insurers must typically renew group coverage at the option of the employer or plan sponsor. However, HIPAA provides a few limited exceptions where renewal may legally be denied.

One of these exceptions occurs when the employer or group policyholder fails to comply with the insurer’s participation or employer contribution requirements . Participation rules usually require a minimum percentage of eligible employees to enroll in the plan, while contribution rules require the employer to pay a specified portion of the premium. If the employer fails to meet these requirements or violates the contractual conditions, the insurer may have grounds to deny renewal of the group policy .

The other choices are incorrect. HIPAA does not allow insurers to deny renewal simply because the group had high claims experience , because the group size increased , or because contribution rules were changed . The critical factor is violation of participation or contribution requirements , making Option C the correct answer.