The given trinomial can be factored using factorization as
x²-x-12
=x²-4x+3x-12
=x(x-4)+3(x-4)
=(x-4)(x+3)
Thus x-4 and x+3 are the factors of the given trinomial. From these we can see x+3 is listed in option A
So the answer to this question is Option A