詳解：根據多項式的反微分規則

\(\int {{x^n}dx}  = \left\{ {\begin{array}{*{20}{c}}{\frac{1}{{n + 1}}{x^{n + 1}} + C\quad ,n \ne  - 1}\\{\quad \quad \ln x\quad \quad \quad ,n =  - 1}\end{array}} \right.\)

\(\int {\sqrt x \;dx}  = \int {{x^{\frac{1}{2}}}\;dx}  = \frac{2}{3}{x^{\frac{3}{2}}} + C\)

故選(A)