Đẳng thức nào dưới đây là đúng?

\((A)\,\left( { - 3{x^{2n}}{y^n}{z^n}} \right)\)\(:\left( { - \dfrac{3}{5}{x^n}{y^{n - 1}}{z^{n - 3}}} \right)\)

\( = \left[ {\left( { - 3} \right):\left( { - \dfrac{3}{5}} \right)} \right]\)\(.\left( {{x^{2n}}:{x^n}} \right).\left( {{y^n}:{y^{n - 1}}} \right).\left( {{z^n}:{z^{n - 3}}} \right)\)

\( = \left( { - 3} \right).\left( {\dfrac{{ - 5}}{3}} \right).{x^{2n - n}}.{y^{n - \left( {n - 1} \right)}}\)\(.{z^{n - \left( {n - 3} \right)}}\)

\(= 5{x^n}y{z^3}\)

\((B)\,\left( { - 3\dfrac{1}{4}{x^{2n + 1}}{y^{n - 2}}{z^{n + 4}}} \right)\)\(:\left( { - 5\dfrac{3}{4}{x^{n - 1}}{y^{n - 3}}{z^{n - 2}}} \right)\)

\( = \left[ {\left( { - 3\dfrac{1}{4}} \right):\left( { - 5\dfrac{3}{4}} \right)} \right]\)\(.\left( {{x^{2n + 1}}:{x^{n - 1}}} \right)\)\(.\left( {{y^{n - 2}}:{y^{n - 3}}} \right).\left( {{z^{n + 4}}:{z^{n - 2}}} \right)\)

\( = \left[ {\left( {\dfrac{{ - 13}}{4}} \right):\left( {\dfrac{{ - 23}}{4}} \right)} \right]\)\(.{x^{2n + 1 - \left( {n - 1} \right)}}.{y^{n - 2 - \left( {n - 3} \right)}}.{z^{n + 4 - \left( {n - 2} \right)}}\)

\(= \left( {\dfrac{{ - 13}}{4}.\dfrac{{ - 4}}{{23}}} \right).{x^{n + 2}}y.{z^6}\)

\( = \dfrac{{13}}{{23}}{x^{n + 2}}y{z^6}\)

\((C)\,\left( {\dfrac{2}{5}{x^6}{y^3}{z^4}} \right)\)\(:\left( { - \dfrac{3}{{25}}{x^2}y{z^4}} \right)\)

\( = \left[ {\dfrac{2}{5}:\left( {\dfrac{{ - 3}}{{25}}} \right)} \right]\)\(.\left( {{x^6}:{x^2}} \right).\left( {{y^3}:y} \right).\left( {{z^4}:{z^4}} \right)\)

\( = \dfrac{2}{5}.\dfrac{{ - 25}}{3}.{x^{6 - 2}}.{y^{3 - 1}}.{z^{4 - 4}}\)

\( = \dfrac{{ - 10}}{3}{x^4}{y^2} \)

\(=  - 3\dfrac{1}{3}{x^4}{y^2}\)

\((D)\,5{x^9}{y^5}{z^3}\)\(:\left( { - \dfrac{2}{3}{x^5}{y^4}{z^2}} \right)\)

\( = \left( {5:\dfrac{{ - 2}}{3}} \right).\left( {{x^9}:{x^5}} \right)\)\(.\left( {{y^5}:{y^4}} \right).\left( {{z^3}:{z^2}} \right)\)

\( = 5.\dfrac{{ - 3}}{2}.{x^{9 - 5}}.{y^{5 - 4}}.{z^{3 - 2}}\)

\( = \dfrac{{ - 15}}{2}{x^4}yz \)\(=  - 7\dfrac{1}{2}{x^4}yz\)