28) air can be considered a mixture. which statement describe air? a) air contains a fixed ratio of atoms. b) the components of air separate into visible layers. c) the components of air can be separated by chemical means. d) the exact mixture of components varies from point to point.

Explanation:

It's important to know that the air is a mixture formed by around 78% of nitrogen, 21% of oxygen, 0.9% of argon, 0.04% of carbon dioxide, and other gases in smaller amounts.

Additionally, the mixture that formed the air is not always the same, it variates depending on several variables, that means the air as such can slightly change is mixture, at some points can have a bit more oxygen or a bit more carbon dioxide. In other words, the air is not a constant mixture.

Having said that, the right answer is D, because the mixture of components can actually vary from point to point.