Final answer:
An offer in the context of a legal contract refers to a proposal made by one party to another, as demonstrated by sellers presenting a warranty or service contract that becomes binding upon acceptance by the buyer.
Step-by-step explanation:
Based on the definition of a legal contract, an offer is best represented by the statement: A proposal made by one party to another. This is because an offer is an expression of willingness to contract on certain terms, made with the intention that it shall become binding as soon as it is accepted by the person to whom it is addressed. For instance, sellers may offer a warranty or a service contract as part of a transaction, which exemplifies a proposal that becomes an agreement once the buyer accepts by paying the extra amount for the service contract.