Final answer:
When a set of positive integers has no prime factors in common, the Greatest Common Factor (GCF) is 1.
Step-by-step explanation:
If a set of positive integers has no prime factors in common, the Greatest Common Factor (GCF) is 1. This is because the GCF is the largest positive integer that divides each of the integers in the set without leaving a remainder. Since the integers do not share any prime factors, the only factor they all have in common is 1, meaning the GCF must be 1.
The correct answer cannot be a product or sum of the numbers (options A and B), nor can it be calculated as a function of the product (option C), nor is it correct to subtract one from their product (option D). Therefore, none of the options A to D correctly describes the GCF when there are no common prime factors.