$$\frac{2+\sqrt{3}}{2-\sqrt{3}}+\frac{2-\sqrt{3}}{2+\sqrt{3}}+\frac{\sqrt{3}+1}{\sqrt{3}-1}$$ = 

A

$$16 + \sqrt{3}$$

B

$$4 - \sqrt{3}$$

C

$$2 - \sqrt{3}$$

D

$$2 + \sqrt{3}$$