Đáp án đúng: A
Na, K, mNa = 4,6 gam; mK = 3,9 gam.
$\displaystyle \begin{array}{l}{{\text{n}}_{\text{A+B}}}\,\text{=}\,\text{2}{{\text{n}}_{{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}}}\,\text{=}\,\text{2}\text{.0}\text{,3}\text{.0}\text{,5}\,\text{=}\,\text{0}\text{,3}\\\Rightarrow \,{{\text{M}}_{\text{AB}}}\,\text{=}\,\frac{\text{8}\text{,5}}{\text{0}\text{,3}}\,\text{=}\,\text{28}\text{,33}\,\Rightarrow \,\text{K}\text{,}\,\text{Na}\\\left\{ \begin{array}{l}{{\text{n}}_{\text{Na}}}\,\text{+}\,{{\text{n}}_{\text{K}}}\,\text{=}\,\text{0}\text{,3}\\\text{23}{{\text{n}}_{\text{Na}}}\,\text{+}\,\text{39}{{\text{n}}_{\text{K}}}\,\text{=}\,\text{8}\text{,5}\end{array} \right.\,\Rightarrow \,\left\{ \begin{array}{l}{{\text{n}}_{\text{Na}}}\,\text{=}\,\text{0}\text{,2}\\{{\text{n}}_{\text{K}}}\,\text{=}\,\text{0}\text{,1}\end{array} \right.\Rightarrow \left\{ \begin{array}{l}{{\text{m}}_{\text{Na}}}\,\text{=}\,\text{4}\text{,6}\\{{\text{m}}_{\text{K}}}\,\text{=}\,\text{3}\text{,9}\end{array} \right.\end{array}$
