The question should explicitly state the type of compounding (simple, complex, or continuous - corresponding to your examples 2, 1, 3, respectively). I have found that the type of compounding is not always stated explicitly for questions in this course; however, the difference in the solutions is always much smaller than the spread in values of the multiple choice answers (i.e. it doesn't matter which form you use.)
[NEAS: Correct. For multiple choice questions, all three methods give the same solution.]