Đáp án đúng: B
Giải chi tiết:\(\left\{ \begin{gathered} 2.(2{p_M} + {n_M}) + (2{p_X} + {n_X}) = 140\,\,\,\,\,\,\,\,\,\,\,\,\,(1) \hfill \\ (2.2{p_M} + 2{p_X}) - (2{n_M} + {n_X}) = 44\,\,\,\,\,\,\,\,\,\,\,\,(2) \hfill \\ ({p_M} + {n_M}) - ({p_X} + {n_X}) = 23\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(3) \hfill \\ (2{p_M} + {n_M}) - (2{p_X} + {n_X}) = 34\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(4) \hfill \\ \end{gathered} \right.\)
Lấy (1)+(2) => 8pM + 4pX = 184
Lấy (4)-(3) => pM - pX = 11
\(\left\{ \begin{gathered} 8{p_M} + 4{p_X} = 184 \hfill \\ {p_M} - {p_X} = 11 \hfill \\ \end{gathered} \right. \to \left\{ \begin{gathered} {p_M} = 19 \hfill \\ {p_X} = 8 \hfill \\ \end{gathered} \right.\)
=> M là K, X là O => K2O
Đáp án B