Some steps to rewrite the expression x^3 − 9x + x^2 − 9 as a product of three factors are shown below:

step 1: x^3 − 9x + x^2 − 9
step 2: x^3 + x^2 − 9x − 9
step 3: x^2(x + 1) − 9(x + 1)

which of the following best shows the next two steps to rewrite the expression?
a) step 4: (x^2 + 9)(x + 1); step 5: (x + 3)(x + 3)(x + 1)
b) step 4: (x^2 − 9)(x + 1); step 5: (x + 3)(x + 3)(x + 1)
c) step 4: (x^2 + 9)(x + 1); step 5: (x − 3)(x + 3)(x + 1)
d) step 4: (x^2 − 9)(x + 1); step 5: (x − 3)(x + 3)(x + 1)