D. Grey

According to Treas. Regs. 1.410(b)-4(c)(2) as long as the plan satisfies the “Ratio Percentage Test” — meaning that the percentage of the non-highly compensated employees benefiting under the plan equal at least 70 percent of the percentage of the employer's highly compensated employees benefiting under the plan any category of employees may be excluded. If you can't pass this test I would be cautious. In that case employment categories should not indicate length of service, such as "seasonal employees" but rather a job description that serves a bone fide business purpose such as "employees at the New Brunswick plant" or "life guards".