If the coefficient of $$x^7$$ in $$\left[ax^2 + \left(\frac{1}{bx}\right)\right]^{11}$$ equals the coefficient of $$x^{-7}$$ in $$\left[ax^2 - \left(\frac{1}{bx}\right)\right]^{11}$$, then $$a$$ and $$b$$ satisfy the relation

A

$$a - b = 1$$

B

$$a + b = 1$$

C

$$\frac{a}{b} = 1$$

D

$$ab = 1$$