Which of these number systems uses the most unique characters?
a
binary

b
decimal

c
hexadecimal

i say hexadecimals

Explanation:

The hexadecimal numeral system, often shortened to "hex", is a numeral system made up of 16 symbols (base 16). The standard numeral system is called decimal (base 10) and uses ten symbols: 0,1,2,3,4,5,6,7,8,9. Hexadecimal uses the decimal numbers and six extra symbols.