Final answer:
The modulus operator is used in a program to find the greatest common factor (GCD) of two numbers, commonly through the Euclidean algorithm.
Step-by-step explanation:
The correct answer to the question "A program to find the greatest common factor of two numbers will use" is d) The modulus operator. The modulus operator is used in programming to find the remainder of a division between two numbers. When creating a program to find the greatest common factor, also known as the greatest common divisor (GCD), the modulus operator can be used in an algorithm such as the Euclidean algorithm, which repeatedly applies the modulus operation until the remainder is zero. At that point, the non-zero divisor is the GCD of the two numbers. Object-oriented programming, binary numbers, and a database are not specifically required to perform this task.