\(n_{RO_2}=\dfrac{V}{22,4}=\dfrac{5,6}{22,4}=0,25\left(mol\right)\)
\(\Rightarrow M_{RO_2}=\dfrac{m}{n}=\dfrac{16}{0,25}=64\) (g/mol)
\(\Rightarrow M_R+2M_O=64\)
\(\Rightarrow M_R=64-2.16=32\left(S\right)\)
\(\Rightarrow\)R là S
\(\Rightarrow\)B là SO2