$$\frac{1}{\sqrt{12 - 2\sqrt{35}}} - \frac{1}{\sqrt{8 - 2\sqrt{15}}} - \frac{2}{\sqrt{10 + 2\sqrt{21}}} =$$

A

$$2\sqrt{3}$$

B

$$2\sqrt{5}$$

C

$$2\sqrt{7}$$

D

0