When water moves freely from a membrane containing a higher concentration to a lower concentration, the diffusion is called
a. diffusion
b. osmosis
c. active transport
d. passive transport

The correct answer is B. osmosis

Explanation:

Osmosis is the process by which water molecules move through a semipermeable membrane from area having high concentration of water towards an area having a lower concentration of water.

It can also be said that water diffuses from an area having more solute concentration to an area having lower solute concentration. The process of osmosis is passive which means that it does not require any use of energy. It is a type of diffusion. So the right answer is B. osmosis.