The value of \({\tan ^{ - 1}}\left( {\frac{1}{2}} \right) + {\tan ^{ - 1}}\left( {\frac{1}{3}} \right)\) is

• A. π
• B. \(\frac{\pi }{2}\)
• C. \(\frac{\pi }{3}\)
• D. \(\frac{\pi }{4}\)