The correct answer is:
The GCF.
Explanation:
GCF stands for "Greatest Common Factor." This is by definition the largest of all factors of two or more numbers.
To find the GCF, we first find the prime factorization of each number. This is the list of prime factors that are multiplied to make each number. We then take only the common factors out and multiply them together; this gives us the GCF.
