Final answer:
Profit sharing plans may permit in-service withdrawals after two years of service (option b), but it is not a requirement.
Step-by-step explanation:
Profit sharing plans can have different rules regarding in-service withdrawals. Option A is incorrect because some profit sharing plans do allow in-service withdrawals, although it is not a common feature. Option B is incorrect because there is no standard requirement for profit sharing plans to permit in-service withdrawals after two years of service.
Option C is incorrect because profit sharing plans can allow distributions throughout the employee's tenure, not just at termination. Option D is correct because profit sharing plans may choose to permit in-service withdrawals after two years of service, but it is not a requirement.