Answer: Density, Hardness, Boiling point, Melting Point
Explanation: Physical Properties are those properties which can be measured. These are those observables which can be used to defined to the state of the system and which do not bring any change in the molecular composition of the system.
Whereas Chemical Properties are those which can bring changes in the original identity of the composition.
Out of the given, Density, Hardness, Boiling Point and Melting Point r the properties due to which the physical state of any system can be defined.
Reactivity and Flammability cannot be considered among them.