Answer : The correct option is, (C) decreases
Explanation :
As we know that the density is measured as the mass of substance divided by the volume of substance. The S.I unit of density is, kilogram per cubic meter or

Formula for density :

That means the density is directly proportional to the mass of the substance and inversely proportional to the volume of the substance.
As the volume of substance decreases, the density of a substance will be increases and volume of substance increases, the density of a substance will be decreases.
Hence, the correct option is, (C) decreases