Final answer:
Passive transport includes osmosis, facilitated diffusion, and simple diffusion across the lipid bilayer, all of which move substances down their concentration gradient without energy from the cell. The correct option is 4) All of these
Step-by-step explanation:
Passive transport includes osmosis, facilitated diffusion, and diffusion of a substance directly across the lipid bilayer of the membrane. All of these methods do not require any energy input from the cell and involve the movement of molecules from an area of higher concentration to an area of lower concentration.
Simple diffusion allows gases and small hydrophobic molecules to directly pass through the membrane, while osmosis is specifically the diffusion of water molecules.
Large or hydrophilic molecules and charged ions, on the other hand, require the assistance of transport proteins during facilitated diffusion to move across the membrane. The correct option is 4) All of these