In Bohr's model, the atomic radius of the first orbit is \[{{r}_{0}}\], then the radius of the third orbit is [AIIMS 1997; CPMT 2001; KCET (Engg./Med.) 1999; Pb. PMT 2004]

• A.            \[\frac{{{r}_{0}}}{9}\]       
• B.            \[{{r}_{0}}\]
• C.            \[9{{r}_{0}}\]  
• D.            \[3{{r}_{0}}\]