Correct Answer - Option 4 : Positively and negatively charged sols, respectively
Concept:
Hemoglobin and gold sol both are colloids and always carry an electric charge. Hemoglobin is a positively charged sol, because in hemoglobin, Fe
2+ ion is the central metal ion of the octahedral complex. All metal sols like, Au-sol, Ag-sol etc. are negatively charged sols.