Đáp án đúng: C
Giải chi tiết:\(\begin{array}{l}A = 81.\left( {27 + {9^{15}}} \right):\left( {{3^5} + {3^{32}}} \right)\\\,\,\,\,\,\,\,\,\,\,\,\,\, = {3^4}.\left[ {{3^3} + {{\left( {{3^2}} \right)}^{15}}} \right]:\left[ {{3^5}\left( {1 + {3^{27}}} \right)} \right]\\\,\,\,\,\,\,\,\,\,\,\,\,\, = {3^4}.\left( {{3^3} + {3^{30}}} \right):\left[ {{3^5}\left( {1 + {3^{27}}} \right)} \right]\\\,\,\,\,\,\,\,\,\,\,\,\,\, = {3^4}{.3^3}\left( {1 + {3^{27}}} \right):\left[ {{3^5}\left( {1 + {3^{27}}} \right)} \right]\\\,\,\,\,\,\,\,\,\,\,\,\,\, = {3^7}.\left( {1 + {3^{27}}} \right):\left[ {{3^5}\left( {1 + {3^{27}}} \right)} \right]\\\,\,\,\,\,\,\,\,\,\,\,\,\, = {3^7}:{3^5} = {3^{7 - 5}} = {3^2} = 9.\end{array}\)
Chọn C.