Factorial operation of a number (n!) is the product of all positive integers less than or equal to this number.
For a number n, n! = n x (n - 1) x (n - 2) ... 1.
So, let's evaluate 4!
If n = 4, you have to mulitply it by (n - 1 = 3), (n - 2 = 2) and (n - 3 = 1).
That is:
4! = 4 x 3 x 2 x 1 = 24
Answer: A. 4 x 3 x 2 x 1
