If \[P=\sqrt[3]{\sqrt[3]{{{a}^{9}}}},\]what is the value of p?

• A.  \[{{\left( {{a}^{3}} \right)}^{3}}\]                             
• B.                         \[{{a}^{3}}\]                     
• C.                         \[{{a}^{9}}\]                                     
• D.                         a