What Does It Mean When Reformation Occurs

What does it mean when reformation occurs?

A) An insurer and a policy holder renegotiate the terms of an insurance contract because the risk of providing insurance to the policyholder has changed.
B) A court changes a written insurance policy when there was a mutual mistake or fraud on the part of the insurer so it conforms to the parties' supposed actual agreement
C) An insurance policy holder changes the beneficiary on an insurance policy and the insurer revises the policy contract.
D) An insurance contract is voluntarily reformed or modified by an insurer because of a unilateral mistake on the part of the insured.