Final answer:
According to Dunlap (1998), the Root ZX apex locator is equally accurate in determining the working length in both necrotic and vital canals.
Step-by-step explanation:
The study by Dunlap (1998) examined the accuracy of the Root ZX apex locator in determining the working length of both necrotic and vital canals during endodontic procedures. The findings of the study revealed that the Root ZX is highly accurate in both types of canals, but it did not assert that it was more accurate in one type over the other. Therefore, the correct answer would be (a) Root ZX is equally accurate in necrotic and vital canals.