Answer:
d. substance #5 in a gas at 78' F
Explanation:
Diffusion in substances simply has to do with the movement of the particles of a substance from one point to another.
The rate of diffusion varies in gases, liquids and solids. Gas molecules are usually more energetic than molecules of solids and liquids. Gases and are also in constant random motion at high velocities.
Therefore, substance #5 in a gas at 78' F will have the greatest diffusion rate.