The most accurate answer is: D) In the front of the dictionary.
This question is tricky, as you can confuse it with the marks that come in every definition to help with pronunciation. For example: literature /ˈlɪt̬.ɚ.ə.tʃɚ/
But the key to pronunciation marks is the guide that teaches you how to use those marks, In general they come at the beggining of the dictionary (in my dictionay it comes in the second page and it is titled "Key to the symbols used in the respelling for pronunciation"). If we had only the marks without any guide, we could not be able to undestand them and therefore they wold be useless.