Answer: Unilateral contract.
Explanation:
A unilateral contract is a contract in which promise to fulfill a requirement is made only in one direction, when only the offeror makes a promise and the offeree is on the receiving end of the promise. In insurance the insurer is the only one who makes a promise while the insured is the one receiving the offer(and can break from the agreement at any time).The insurer is the offeror while the insured is the offeree.