Final answer:
M's son is a revocable beneficiary of the Accidental Death and Dismemberment (AD&D) policy because M can change the beneficiary designation at any time without the son's consent.
Step-by-step explanation:
If M has the right to change the beneficiary designation at any time, his son is a revocable beneficiary. This means that M can change the beneficiary without the son's consent.
The other types of beneficiaries are not correct in this context: a tertiary beneficiary is a third in line to receive the benefits, an irrevocable beneficiary cannot be changed without the beneficiary's consent, and a contingent beneficiary is one who will receive the benefits if the primary beneficiary is unable to do so.
The statement accurately describes the concept of a revocable beneficiary and contrasts it with other types of beneficiaries in the context of life insurance or similar financial instruments. In this scenario, M, as the policyholder, retains the right to change the beneficiary designation at any time without requiring the son's consent.
The definitions provided for tertiary, irrevocable, and contingent beneficiaries are also correct in their respective contexts.