Binary is the correct answer because computers use the binary system, which consists of just two numbers, 0 and 1, to represent data and carry out operations. In binary, each digit represents a power of 2. Decimal, while commonly used in everyday life, represents numbers in base 10 and is not directly used by computers for operations. Hexadecimal is often used to represent binary data in a more human-readable form, but it is not the primary system computers use to process data.