The flocculation values (in mmol per litre) of $\mathrm{KCl}$, $\mathrm{K}{}_2\mathrm{SO}{}_4$ and $\mathrm{K}{}_3[\mathrm{Fe}(\mathrm{CN}){}_6]$ for a certain sol are 100, 0.65 and 0.09 respectively. The sol is:

1. Anegatively charged, because the coagulating power rises with the charge of the anion
2. Bpositively charged, because the coagulating power rises with the charge of the anion
3. Celectrically neutral, because the flocculation values differ widely
4. Dnegatively charged, because $\mathrm{K}{}^{+}$ is common to all three salts