A subscription policy is used when a single insurance risk is too large for one insurer to assume alone. Multiple insurers participate in the policy, each taking a percentage of the risk. Because each insurer is directly responsible for its portion, the policy must be signed by each participating insurer, acknowledging its share of liability.

Option A, prescription, refers to legal limitation periods.

Option B, all-inclusive, is not a recognized type of policy requiring multiple insurer signatures.

Option D, subrogation, is a legal right---not a policy type.

Only the subscription policy requires signatures from all insurers involved, making C correct.