Đáp án đúng: C
Giải chi tiết:\(\begin{array}{l}B = \left( {{2^8} + {8^3}} \right):\left( {{2^5}{{.2}^3}} \right)\\\,\,\,\,\,\,\,\,\,\,\,\, = \left[ {{2^8} + {{\left( {{2^3}} \right)}^3}} \right]:{2^{5 + 3}}\\\,\,\,\,\,\,\,\,\,\,\,\, = \left( {{2^8} + {2^9}} \right):{2^8}\\\,\,\,\,\,\,\,\,\,\,\,\, = {2^8}\left( {1 + 2} \right):{2^8}\\\,\,\,\,\,\,\,\,\,\,\,\, = 1 + 2 = 3.\end{array}\)
Chọn C.