ANS:C - both (a) & (b)

Optical activity is not an additive property, so it would not be correct to explain it as "both (a) & (b)." Let me clarify:

• Additive properties are those that depend on the quantity or amount of a substance, where the property of a mixture is the sum of the properties of its individual components. Examples of additive properties include mass, volume, and energy.
• Constitutive properties, on the other hand, are inherent to the material itself and are not additive. They describe the fundamental characteristics or behavior of the material, often related to its molecular or atomic structure. Optical activity, which arises from the arrangement of molecules in a substance and their interaction with light, is an example of a constitutive property.