Factor the expression below.
3k +9
A:3(3k +9)
B:12k + 9
C:3(k + 3)
D;6(k+2)

Sanderson is having trouble with his assignment. his shown work is as follows: − 3 7 7 3 = − 3 7 × 7 3 = − 21 21 = −1 however, his answer does not match the answer that his teacher gives him. complete the description of sanderson's mistake. find the correct answer.