( x + 1/x ) ( x - 1/x ) ( x^2 + 1x^2 - 1 ) ( x^2 + 1x^2 + 1 ) is equal to ?

Answer: Option A

Given expression,
$$\left[\left(x+\frac{1}{x}\right)\left(x^2+\frac{1}{x^2}-x.\frac{1}{x}\right)\right]$$     $$\left[\left(x-\frac{1}{x}\right)\left(x^2+\frac{1}{x^2}+x.\frac{1}{x}\right)\right]$$
$$\begin{array}{rl}& =\left(x^3+\frac{1}{x^3}\right)\left(x^3-\frac{1}{x^3}\right)\\ & =x^6-\frac{1}{x^6}\end{array}$$