In the Context of Generating New Ideas, Which of the Following

In the context of generating new ideas, which of the following is an example of a personal hobby developed into a business venture?

A) A sports card collector becomes a dealer who specializes in the trade of rare and valuable trading cards.
B) A plumber opens a new business that sells piping coated in special anticorrosive paint.
C) A web designer decides to invest in a firm that produces security software.
D) A baker decides to involve various members of his family in the operation of his baking business.