Which of the following is an example of a partnership?

a$.$ Dr$.$ Towerson opens a podiatry business and hires one medical assistant.

b$.$ Dr$.$ Betinini opens a business in a local town.

c$.$ Dr$.$ Nunez and Dr$.$ Spelling open a cardiology business and provide services to their community.

d$.$ Dr$.$ Mann is hired by Northern Spring Hospital to work in the emergency room