Diffusion is not shown by liquids.
Do you know what Diffusion is?
Diffusion is the net movement of molecules or atoms from a region of high concentration (or high chemical potential) to a region of low concentration (or low chemical potential).
Now, think if this happens in liquids.
Can’t think of an example?
Think about releasing a drop of ink in water.
The colour spreads uniformly throughout the water.
Therefore, Liquids diffuse but the diffusion is much slower than gases.