A 5-year-old boy has Healthstar through his father and Medical Mutual through his mother. Which insurance is primary?

In determining which insurance is considered primary when a child has coverage through both parents, specific rules and guidelines must be followed, commonly referred to as the "birthday rule." This rule states that the insurance coverage of the parent whose birthday comes first in the calendar year is designated as primary.

Since the scenario involves the child having Healthstar through the father and Medical Mutual through the mother, if the mother's birthday falls earlier in the year than the father's, Medical Mutual would be the primary insurance. This is consistent with common practices in coordination of benefits, where one plan is responsible for paying claims first, while the other may cover any remaining costs.

The other options do not align with this primary coverage determination; thus, only selecting Medical Mutual as the primary insurance makes sense based on the standard rules governing such situations.