Assertion `:` Demineralised water does not contain any ions.
Reason `:` Permutit process for water softening gives demineralised water.

Answer

d

Explanation

Demineralised water is free from `Ca^(2+)` and `Mg^(2+)` ions. Permutit exchange sodium ions with `Ca^(2+)` and `Mg^(2+)` ions, to give soft water.
`Na_(2)Al_(2)Si_(2)O_(8).xH_(2)O+M_(2)rarrMAl_(2)Si_(2)O_(8).xH_(2)O+2Na[M^(2+)=Ca^(2+) // Mg^(2+)]`