Final answer:
A basic unit of data like a letter, number, or special character is called a A) Character, which is the smallest unit of written language used in computing.
Step-by-step explanation:
A basic unit of data such as a letter, number, or special character is known as a Character. This is the simplest element of written language that has semantic value and is typically coded in computer systems using a set of binary numbers. In a database context, a group of characters forms a Field, which in turn is part of a Record that contains all the data related to one entity.