So, just a note of formatting, to indicate something is an exponent of something else, use the carat (^) sign
for instance
x^3 means x cubed. x3 means 3x.
Anyways, though, let's factor.
You can factor out an x from each variable.
x(x^2-5x-14)
Now, to factor this, think of what will add to -5, and multiply to -14.
-7 and 2 work.
So, this factors out to
x(x-7)(x+2)
Choice D is the correct factorization.