Question

the diffusion of water across a selectively permeable membrane is
called facilitated diffusion.
called active transport.
a rare occurrence.
called osmosis.
always beneficial to a cell.

Explanation:

To solve this, we analyze each option:

• Facilitated diffusion involves transport proteins for molecules (not just water), so the first option is wrong.
• Active transport requires energy and moves against concentration gradients, not matching water diffusion, so the second option is wrong.
• Water diffusion across a selectively permeable membrane is common (osmosis in cells, etc.), so the third option is wrong.
• Osmosis is defined as the diffusion of water across a selectively permeable membrane, so the fourth option is correct.
• Osmosis isn't always beneficial (e.g., cell lysis in hypotonic solutions), so the fifth option is wrong.

Answer:

D. called osmosis.