Answer: The second option would be the answer
Explanation:
Factoring the number is just listing all the whole numbers it can be divided by, and in this case it includes the variable. 16a is dividable by 1, 2, 4, 8, 16, and a; since 16a / a = 16. Apply this to 18b, and 1, 2, 3, 6, 9, 18, and b.