If the arithmetic mean of two surds is $$5 + 9\sqrt{2}$$ and one of them is $$1 + 12\sqrt{2}$$, then the square root of the second surd is

A

$$\sqrt{2} + \sqrt{6}$$

B

$$\sqrt{6} - \sqrt{3}$$

C

$$\sqrt{6} + \sqrt{3}$$

D

$$\sqrt{3} + \sqrt{5}$$