Answer: Option (C) is the correct answer.
Step-by-step explanation:
Chemical property is defined as the property that causes a change in chemical composition of a substance.
For example, toxicity, reactivity, combustibility etc are chemical properties.
Physical property is defined as the property that causes no change in chemical composition of a substance.
For example, melting point, boiling point, mass, volume etc are physical properties.
Therefore, we can conclude that they are unreactive is a chemical property of the noble gases.