There are two equations given in the question and these two equations have to be multiplied.
f(x) = _4x _ 2
And
g(x) = 2x
Then
f (x).g (x) = (-4x-2).2x
f (x).g (x) = -4x.2x - 2.2x
f (x).g (x) = -8x^2 - 4x
From the above deduction, it can be easily concluded that the correct option among all the options that are given in the question is the second option or option "B".