An example of a positively charged sol is

Colloidal solutions are divided into positively charged and negatively charged colloids depending on the type of charge on the particles of the dispersed phase. 

Here are some typical examples: 

Positively charged colloids are : Metal hydroxides $\mathrm{Al}(\mathrm{OH}{)}_3,\mathrm{Fe}(\mathrm{OH}{)}_3,\mathrm{Metaloxide}:{\mathrm{TiO}}_2$, Basic dyes: Methylene blue, Haemoglobin.

Hence the correct option is (C).