The correct answer is D because the behavior described shows that benefit coverage is ending immediately on the employee's termination date rather than continuing through the end of the month. In Workday, this outcome is controlled by the Coverage End Date setting on the termination event within the Enrollment Event Rule. If that setting is configured as On the Event Date, coverage ends on the exact date of termination, which explains why benefits become inactive right away.

Option C is incorrect because if the Coverage End Date were set to Last Day of the Month, the employee's benefits would remain active until the month-end, which is the desired result. Option A is not the best answer because a half-month rule would produce a different timing result and would not directly explain coverage ending exactly on the termination date. Option B is also incorrect because an end date based on the next pay period begin date would not typically cause immediate termination-date inactivation. Since the system is ending benefits on the termination date itself, the termination event rule is clearly set to On the Event Date.