Hướng dẫn giải

- Theo bài ra ta có: $\begin{align}&{{\text{d}}_{{}^{\text{A}}/{}_{\text{C}{{\text{H}}_{\text{4}}}}}}\text{=}\frac{{{\text{M}}_{\text{A}}}}{{{\text{M}}_{\text{C}{{\text{H}}_{\text{4}}}}}}\text{=1,875}\\&\Rightarrow{{\text{M}}_{\text{A}}}\text{=}{{\text{M}}_{\text{C}{{\text{H}}_{\text{4}}}}}\text{.1,875=}\left( \text{12+4} \right)\text{.1,875=30 g/mol} \\ \end{align}$

$\to $ B là khí NO

 Chọn đáp án B.