68.
The answer is: D
Explanation
The correct option is D: Contract.
According to Section 2 (h) of the Indian Contract Act, 1872, a contract is defined as an agreement enforceable by law. This means that a contract is a combination of two elements: an agreement and legal enforceability. An agreement is formed when there is an offer by one party and acceptance by another party. Legal enforceability means that the parties are bound by the law to perform their obligations under the contract, and if they fail to do so, they can be sued for breach of contract.
Therefore, an agreement enforceable at law is a contract.