The correct answer is C. The first example cannot be correct because the colon simply doesn't fit there - a comma would fit better. The second one is also incorrect as you don't need to put a colon after every word, just once before the first word. The last example also doesn't need a colon, you can just enumerate these various states without the use of colon. So naturally, we are left with only one option, and that is C.
C shows the correct use of the colon. After the colon you may express a list.
You might question why D is not correct too. It is not correct because the colon is not needed in that sentence. You are stating the four states you visited, not expressing them as a list.
