\[\sqrt{2}+\sqrt{3}+\sqrt{4}+\sqrt{6}\] is equal to [IIT 1966, 1975]

• A. \[\cot 7\frac{{{1}^{o}}}{2}\]
• B. \[\sin 7\frac{{{1}^{o}}}{2}\]
• C. \[\sin \,{{15}^{o}}\]
• D. \[\cos \,\,{{15}^{o}}\]