An insurance contract is described as unilateral because:

Why A is correct

A unilateral contract is one in which only one party makes a legally enforceable promise. In insurance, the insurer promises to pay covered claims, while the insured's obligation to pay premiums is treated as a condition of coverage rather than a contractual promise the insurer can sue to enforce. This is different from a bilateral contract such as a typical sales agreement, in which both sides exchange enforceable promises. The insured is free to stop paying premiums and let the policy lapse without being sued for breach of contract.

Why the other options are wrong

• B) It is the insurer, not the insured, whose promise is enforceable. The insured is not contractually required to keep the policy in force. The insured is not required to keep the policy and may simply stop paying, while the insurer's promise is enforceable.
• C) Simultaneous performance describes a commutative contract, not an insurance policy. Insurance performance depends on a future uncertain event rather than a simultaneous exchange. Simultaneous exchange describes a commutative bargain; insurance pays only if a future uncertain event occurs.
• D) Notarization is never a general contract requirement. Insurance policies are valid written contracts without any notary seal. A notary is not part of contract formation, and insurance policies are fully valid without notarization.

Memory hook

Unilateral = one promise that binds. The insurer promises; the insured just pays to stay in the game.