Which One of the Following Is the Best Definition of a Contract

Which one of the following is the best definition of a contract food supplier?

A) A business that operates an outside catering service and is called in for special events.
B) A service provided by the employer in-house where hospitality is required.
C) A service provider to a business that needs to provide hospitality but does not want to do it themselves.
D) A provider who sub-contracts the catering to other people before then reselling it to another provider.