In the effect of temperature on density of a substance, ___

Density is defined as the mass per unit volume occupied by the substance.

$\mathrm{Density} =\frac{\mathrm{Mass}}{\mathrm{Volume}}$

As an object is heated, the molecules accelerate and disperse slightly, taking up more space and causing a decrease in density.

As the object cools, the molecules slow down and come close together, resulting in smaller volume and an increased density.

Hence, $\mathrm{Density}\propto \frac{1}{\mathrm{Temperature}}$

Thus, the correct option is D.