Đáp án đúng: D FeCl3 và H2SO4. $\begin{array}{l}\text{3}{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{5}}}\text{N}{{\text{H}}_{\text{2}}}\,\text{+}\,\text{FeC}{{\text{l}}_{\text{3}}}\,\text{+}\,\text{3}{{\text{H}}_{\text{2}}}\text{O}\,\xrightarrow{{}}\,\text{3}{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{5}}}\text{N}{{\text{H}}_{\text{3}}}\text{Cl}\,\text{+}\,\text{Fe(OH}{{\text{)}}_{\text{3}\,}}\\{{\text{2C}}_{\text{2}}}{{\text{H}}_{\text{5}}}\text{N}{{\text{H}}_{\text{2}}}\,\text{+}\,{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\,\xrightarrow{{}}\,{{\text{(C}{{\text{H}}_{\text{3}}}\text{N}{{\text{H}}_{\text{3}}}\text{)}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\end{array}$