Answer: B. Proteins
In contrast to carrier proteins, channel proteins simply form open pores in the membrane, allowing small molecules of the appropriate size and charge to pass freely through the lipid bilayer.
A nucleus, as related to genomics, is the membrane-enclosed organelle within a cell that contains the chromosomes.
A carbohydrate is a type of molecule that contains carbon, hydrogen, and oxygen.
A vacuole is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells.