What feature of a 401(k) plan distinguishes it from a plain profit-sharing plan?

Answer: C. A 401(k) is a defined contribution plan carrying an elective deferral feature, so employees may choose to put part of their pay into the plan. Employer-only funding describes a plain profit-sharing plan, a stated benefit describes a defined benefit plan, and the employee threshold belongs to SIMPLE plans.Source: IRS Publication 560 — Pub 560, Elective deferrals