Correct option is D
Pair (a) is incorrectly matched.
Redox reactions involve both reduction (gain of electrons) and oxidation (loss of electrons). The term "redox" itself is derived from "reduction" and "oxidation." Therefore, associating redox reactions with only reduction is incorrect.
Pair (b) is incorrectly matched.
Density is an intensive property, meaning it does not depend on the amount of substance. Extensive properties, on the other hand, depend on the quantity of the substance, such as mass and volume.
Pair (c) is incorrectly matched.
Volume is an extensive property because it depends on the amount of the substance present. Intensive properties, such as temperature and density, do not depend on the substance's quantity.
Pair (d) is correctly matched.
The first law of thermodynamics, also known as the law of energy conservation, states that the total energy of an isolated system remains constant; it can neither be created nor destroyed, only transformed from one form to another. This principle applies universally, implying that the total energy of the universe is constant.
