Which one of the following statements about air is correct ?

Air is a mixture of several gases, primarily Nitrogen (approximately 78%) and Oxygen (approximately 21%), along with Argon (0.9%), Carbon dioxide (0.04%), and trace amounts of other gases and water vapor. It is classified as a mixture rather than a compound because its components are not chemically bonded in fixed proportions and they retain their individual chemical properties. These components can be separated by physical processes such as fractional distillation of liquid air. Option A is incorrect because a compound consists of elements chemically combined in a fixed ratio. Option C is incorrect because an element consists of only one type of atom. Option D is incorrect because Nitrogen is significantly more abundant in the atmosphere than Oxygen.