Employer group health plans that have 100 or more enrolled employees are required to provide primary disability coverage for disabled employees who are below the age of and have not retired.

The correct answer is 65.

Explanation:

If you have a job enrolling in Medicare during a valid Medicare enrollment period, and you have both Medicare and your employer's insurance, these are the rules set by Medicare that decide which coverage you must pay first (called the "primary payer") and what coverage you must pay in the second instance (called "secondary payer"). Generally, the order of payers works as follows:

If you have retiree coverage from your employer or union, Medicare usually pays first. If your group health plan coverage comes from your current job (or if you got it from a family member), the primary and secondary payer are determined based on your age, the number of people employed by your employer and the reason you have Medicare, either because of your age, disability, or End-Stage Renal Disease (ESRD). If you are under 65 and have a disability, and you or a family member is still working, your group health plan pays first if any of your employers has 100 or more employees. If you are over 65 and you or your spouse are still working, your group health plan pays first if any of your employers has 20 or more employees. If you have Medicare because of an ESRD, your group insurance plan pays first for the first 30 months after you become eligible for Medicare. Medicare will pay first after the 30-month period. Typically, liability insurance, no-fault insurance (including auto insurance), pneumoconiosis benefits, and worker's compensation pay first for your related coverage. Medicaid never pays first for Medicare-covered services, but only pays after Medicare, employer group health plans, and / or Medigap (Medicare supplement) plans have paid.

The answer is letter a