Osmosis is the process in which _______ diffuses across a cell membrane.

a. water
b. energy
c. protein
d. oxygen

I think its a

Right.

Thank you :)

You're welcome.

You are correct! Osmosis is the process by which water molecules diffuse across a cell membrane. Water has the ability to move freely through the phospholipid bilayer of the cell membrane, driven by the concentration gradient of solutes. It moves from an area of lower solute concentration (hypotonic) to an area of higher solute concentration (hypertonic) until equilibrium is reached. This movement of water helps to maintain the balance of water and solutes inside the cell.