The maximum prescribed concentration of cadmium in drinking water in $\mathrm{ppm}$ is

A water sample has ppm level concentration of following anions

 ${\mathrm{F}}^{-}=10 ; {{\mathrm{SO}}_4}^{2- }=100 ; {{\mathrm{NO}}_3}^{-}=50$

The anion/anions that make/makes the water sample unsuitable for drinking is/are.

The recommended concentration of fluoride ion in drinking water is up to$1 \mathrm{ppm}$ as fluoride ion is required to make teeth enamel harder by converting $[3 {\mathrm{Ca}}_3({\mathrm{PO}}_4{)}_2.\mathrm{Ca}\left(\mathrm{OH}{)}_2\right]$ to.