Hexadecimal digits represented 0 to 9 and A to:

The correct answer is B, F. The hexadecimal system has base sixteen, so it needs sixteen symbols for a single place. The digits 0 to 9 give the first ten values and the letters A to F stand for the remaining six, with A as 10, B as 11, C as 12, D as 13, E as 14 and F as 15. One hexadecimal digit therefore holds exactly four bits, which is why memory addresses, colour codes such as FF0000 for red and machine code are written in hex: a long binary string becomes short and easy to read. Option A is wrong because stopping at C would give only thirteen symbols, too few for base sixteen. Option C is wrong because stopping at B leaves twelve. Option D is wrong because stopping at D leaves fourteen, still short of sixteen. Exam tip: binary base 2, octal base 8 using 0 to 7, hexadecimal base 16 using 0 to 9 and A to F.