What characteristic of an insurance contract requires the insured to accept terms without modification?

The correct choice is related to the nature of insurance contracts known as "Contracts of Adhesion." This term specifically refers to the characteristic that such contracts are drafted by one party (the insurer) and offered to the other party (the insured) on a "take-it-or-leave-it" basis. This means that the insured must accept the terms as they stand, without any opportunity to negotiate or modify the provisions.

Contracts of adhesion are typically used in insurance to ensure a standardized approach, which helps maintain fairness and clarity. The insured does not have the power to alter the contract's essential terms, reflecting the asymmetrical bargaining power between the insurer and the insured. This characteristic is crucial in understanding how insurance agreements are formed and the expectations of both parties involved.

In contrast, while non-negotiable contracts exist, they do not specifically convey the same connotation as contracts of adhesion, which are fundamentally about the lack of negotiation. Mutual agreement implies a negotiation process, which is not the case in adhesive contracts, and standardized contracts suggest uniformity but do not enforce the same mandatory acceptance stance of adhesion contracts.