Sana, You are correct that memorizing the types of estimate ranges is easier than some other complicated formulas. I am not sure about the question you are talking about, but I think any question about estimate types will give you a clue about the answer. Perhaps the words in the question might say Top Down or Bottom Up. Perhaps it might say they project manager has to get an estimate very quickly. Other clues might indicate where you are in the project management process. If you are in initiating phase, then a rough order of magnitude would be the correct choice.
As for additional training, if you are on this discussion, then you might know that PM Prepcast has an exam simulator for purchase. Another source of PMP training that really, in my opinion, makes learning easy is the Head First series.