Answer: d. ability to rust
Explanation: Physical Properties are those properties which does not alter the composition of the substance , which does not changes the mass and in which the chemical identity of the species is retained.
These properties are also known as observable as these can be easily identifies by observation itself.
Out of the given composition, color is most certainly the physical property . Melting point and mass also gets counted in the physical property.
Ability to rust does not include in the physical property as it changes the chemical identity of the species, thus it is always named under the chemical properties.
