Which of the following is a strong electrolyte in solution?
[tex]\mathrm{PbMnO}_4[/tex]
[tex]\mathrm{CH}_3 \mathrm{COOH}[/tex]
[tex]\mathrm{FeCl}_3[/tex]
CdS
[tex]\mathrm{NiC}_2 \mathrm{O}_4[/tex]