A bus plying on a route with published fares constitutes a standing offer (continuous offer) to the public. It is not merely an invitation to treat because the transport operator has demonstrated readiness to be bound by contract - anyone can accept this offer by boarding the bus and paying the fare. Option D correctly identifies this as an offer, while A describes an invitation to treat (preliminary negotiation stage), B refers to information sharing during negotiations, and C indicates a preliminary statement not intended as an offer.