A water sample has ppm level concentration of the following metals: Fe = 0.2; Mn = 5.0; Cu = 3.0; Zn = 5.0. The metal that makes the water sample unsuitable for drinking is

According to the maximum permissible concentration level of metals in drinking water, Zn should be 5, Fe should be 0.2, Mn should be 0.05, and Cu should be 3 ppm. Now, as we can see that Mn concentration in the given water sample is way more than the maximum permissible concentration level, it is the metal that makes the water sample unsuitable for drinking.