Answer:
b) Channel pumps
Explanation:
The channels are the transmembrane proteins that serve in the passive transport of substances down the concentration gradient. The channels can be gated or non-gated. The gated channels are opened and closed in response to certain stimuli such as electrical change.
For example, aquaporins are the gated water channels that transport the water across the plasma membrane. The process is driven by the osmotic gradient and does not use the energy of ATP.
It is known as a concentration gradient which in diffusion will always flow from ares of high concentration to areas of low concentrations
So i believe the answer to this is A.
For example salt in water ,salt would dissolve ,you won't be able to see it but if you taste it it would still be there
dissolve /disappear but still be there
