Answer:
D. The air we breathe is a homogeneous mixture because it has substances but the same appearance throughout.
Step-by-step explanation:
The air we breathe is a homogeneous mixture.
Air is a mixture of many gases. A homogeneous mixture is one whose constituents exists in one phase.
Air is a gas - gas mixtures.
A mixture has indefinite composition. They consist of two or more elements and or compounds in any proportion by mass.
Constituents retain their identities i.e. physical properties are retained.