Final answer:
Option B is an offer, as it is a clear promise of payment in exchange for a specific action, creating a unilateral contract upon the action's completion. The other options are invitations to treat, which indicate a willingness to enter into negotiations rather than establishing a firm offer.
Step-by-step explanation:
Understanding whether something is an offer or an invitation to treat is key in contract law. An offer is a definitive promise to be bound, provided that certain terms are accepted. An invitation to treat is merely an expression of willingness to negotiate a contract.
In the scenarios provided, option B is an offer: "I will pay $100 to whomever finds and returns my lost female calico cat who answers to the name Marx." This statement indicates a clear intention to be bound by the terms proposed upon them being fulfilled. The person making the statement is offering payment in return for a specific action, which creates a unilateral contract once someone chooses to perform the requested action (i.e., finding and returning the cat).
Options A, C, D, and E are considered invitations to treat. These postings are not offers because they do not contain a commitment to be bound without further negotiation. They merely show a willingness to discuss and possibly enter into a contract. Option A is an advertisement for a sale, not an offer to sell at a specific price to a specific person. Option C is a display of goods which invites customers to make an offer to purchase. Option D is similar, where the price tag is an invitation for customers to make an offer at the cash register. Option E is an advertisement likely encouraging offers on a property, but it is not in itself a legally binding offer.