Which of the following is not an example of a barrier to entry?
A. Mighty Mitch’s Mining Company owns a unique plot of land in Tanzania, under which lies the only large deposit of Tanzanite in the world.
B. A college student starts a part-time tutoring business.
C. A novelist obtains a copyright for her new book.
D. A taxi cab driver in New York City obtains a license to legally provide transportation in New York City.