Hướng dẫn:

${{m}_{A}}={{m}_{{{O}_{2}}}}+{{m}_{{{N}_{2}}}}={{n}_{{{O}_{2}}}}.{{M}_{{{O}_{2}}}}+{{n}_{{{N}_{2}}}}.{{M}_{{{N}_{2}}}}=0,2.32+0,15.28=10,6\left( g \right)$

${{n}_{A}}={{n}_{{{O}_{2}}}}+{{n}_{{{N}_{2}}}}=0,2+0,15=0,35\left( mol \right)$

${{\bar{M}}_{A}}=\frac{{{m}_{A}}}{{{n}_{A}}}=\frac{10,6}{0,35}\approx 30,29$

${{d}_{A/C{{O}_{2}}}}=\frac{{{{\bar{M}}}_{A}}}{{{M}_{C{{O}_{2}}}}}=\frac{30,29}{44}=0,69$

$\Rightarrow $ Chọn đáp án D