2. The value of $\sqrt{\sqrt{2+\sqrt{3}}+\sqrt{2-\sqrt{3}}}$ is ( ).
(A) $\sqrt{6}$
(B) $2 \sqrt{6}$
(C) 6
(D) $\sqrt[4]{6}$
2. D
2. $(\sqrt{2+\sqrt{3}}+\sqrt{2-\sqrt{3}})^{2}=6$.

Translate the above text into English, please retain the original text's line breaks and format, and output the translation result directly.

2. D
2. $(\sqrt{2+\sqrt{3}}+\sqrt{2-\sqrt{3}})^{2}=6$.