The best answer is C
Carrier and channel proteins are involved in facilitated diffusion.
A carrier protein is a transport protein that is specific to a particular type of ion, molecule or substance.
It is a special protein that binds to a molecule and carries the bound molecule across the cell membrane. The protein changes its shape so that it can fit into the channels that run through the membrane and then goes through the channel with its cargo.
A channel protein is a transport protein on the cell membrane and acts like a pore, allowing ions and small molecules to pass through more efficiently.
