Final answer:
The characteristic not true for gases is formation of homogenous mixtures. Hence the correct answer is option B
Step-by-step explanation:
The correct answer is B. formation of homogenous mixtures.
Gases have the ability to form homogenous mixtures. When gases mix together, they form a solution, which is a homogeneous mixture. For example, air is a solution of mostly nitrogen and oxygen.
The other options listed, A. compressibility and C. expansion to fill their containers, are both characteristics of gases. Gases can be compressed, meaning their volume can be reduced under pressure. Gases also have the ability to expand and fill the entire volume of their container.
Therefore, the characteristic that is not true for gases is formation of homogenous mixtures.