Which of the following statements is true? a. the greatest common factor of 2 or more numbers is the largest prime number that is a divisor of all of the numbers. b. the greatest common factor of 2 or more numbers is the largest number that is not a divisor of all of the numbers. c. the greatest common factor of 2 or more numbers is the smallest number that is a divisor of all of the numbers. d. the greatest common factor of 2 or more numbers is the largest number that is a divisor of all of the numbers.