Ordinary tap water conducts electric current due to ___.

A liquid conducts electricity in it through the passage of free ions in it. Free ions act as charge carriers and move under potential differences, producing an electric current (because the electric current is only the amount of charge flowing through the conductor per second). Free ions are usually produced by the dissociation of a liquid (if ionic) or an ionic salt contained in the liquid. Ionic salts such as sodium chloride dissociate in polar solvents such as water. This creates free ions (cations and anions in the salt) in the liquid. These free ions play a role in conducting electricity. Normal tap water contains a lot of dissolved salts such as chloride salt. These salts produce free ions, which is why ordinary tap water conducts electricity. 

Therefore, the correct option is 1.