The correct answer is B. byte.
A byte is a unit of digital information that most commonly consists of eight bits. A bit is the most basic unit of information in computing and is represented by a 0 or a 1. Bytes are used to represent numbers, letters, and other characters.
The length of a word in a computer is typically measured in bytes. The number of bits in a byte can vary depending on the computer architecture. For example, in a 32-bit architecture, a word is typically 32 bits long. In a 64-bit architecture, a word is typically 64 bits long.
The other options are incorrect. A bit is the most basic unit of information in computing and is represented by a 0 or a 1. A millimeter is a unit of length in the metric system. A metre is a unit of length in the metric system.