The hexadecimal digits are 0-9 and A-_____

The correct answer is "F." In the hexadecimal number system, there are 16 possible digits that can be used to represent a value. Since we only have 10 Arabic numerals (0-9) to work with, we need to use letters to represent the remaining six digits. In hexadecimal notation, after 9 comes A, followed by B, C, D, E, and finally F. So the complete set of hexadecimal digits are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F. Therefore, the correct answer is F.