\(C=\sqrt{11+4\sqrt{6}}-\sqrt{5-2\sqrt{6}}=\sqrt{8+2.2\sqrt{2}.\sqrt{3}+3}-\sqrt{3-2.\sqrt{2}.\sqrt{3}+2}=\sqrt{\left(2\sqrt{2}+\sqrt{3}\right)^2}-\sqrt{\left(\sqrt{3}-\sqrt{2}\right)^2}=\left|2\sqrt{2}+\sqrt{3}\right|-\left|\sqrt{3}-\sqrt{2}\right|=2\sqrt{2}+\sqrt{3}-\left(\sqrt{3}-\sqrt{2}\right)=2\sqrt{2}+\sqrt{3}-\sqrt{3}+\sqrt{2}=3\sqrt{2}\)