Kết quả rút gọn biểu thức$P=\frac{{{{a}^{{\sqrt{5}}}}-{{b}^{{\sqrt{7}}}}}}{{{{a}^{{\frac{{2\sqrt{5}}}{3}}}}+{{a}^{{\frac{{\sqrt{3}}}{3}}}}{{b}^{{\frac{{\sqrt{7}}}{3}}}}+{{b}^{{\frac{{2\sqrt{7}}}{3}}}}}}$ là?
A. ${{a}^{{\sqrt{5}}}}-{{b}^{{\sqrt{7}}}}.$
B. ${{a}^{{\frac{{\sqrt{5}}}{3}}}}-{{b}^{{\frac{{\sqrt{7}}}{3}}}}.$
C. ${{a}^{{\sqrt{5}}}}+{{b}^{{\sqrt{7}}}}.$
D. ${{a}^{{\frac{{\sqrt{5}}}{3}}}}+{{b}^{{\frac{{\sqrt{7}}}{3}}}}.$