Which of the following scenarios constitute an "agreement" and which do not. Explain your answer.

--A driver pulls up to a gas pump and begins dispensing fuel;

--A shopper samples a gumdrop from the bulk food bin at a grocery;

--A driver "test drives" a vehicle, but does not return it (without consent);

--A homeowner calls a plumber for a service call but cancels (after dispatch) before any service is rendered.