C is Correct. A student investing in a yoga business is in effect becoming a business partner. While a financial relationship is not forbidden under the Code of Ethics, it is strongly discouraged because of the very different nature of “student-teacher” and “business partner” relationships and the potential problems that can arise. In this answer Mysti explains to Mark the “sticky issues” and possible consequences of such a dual relationship. This honesty, and Mark proceeding with a different teacher, will keep their business relationship clean and professional.
A, B, D, E are all Incorrect. The other answers all place more importance on Mysti’s interests than on what will best serve Mark, her student. Ideally, teachers place students’ best interests above their own, and always maintain ethical behavior, i.e., do no harm.