Misty Has the Option of Purchasing One of Three Products

Misty has the option of purchasing one of three products: Brand A, Brand B or Brand C. Each costs ten dollars. If she decides that Brand A meets her needs best, then the opportunity cost of this decision is

A) Brand A.
B) Brand B plus Brand C.
C) twenty dollars.
D) Brand B or Brand C, depending on which is considered the highest- value alternative forgone.