Under what condition will diffusion take place most rapidly?

c

movement from an area of high concentration to an area of low concentration

The correct answer is c) movement from an area of high concentration to an area of low concentration. Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. It occurs down the concentration gradient, which means that particles move from an area of high concentration to an area of low concentration until equilibrium is reached. This is the condition under which diffusion will take place most rapidly.

The correct answer is c. Diffusion occurs most rapidly when molecules move from an area of high concentration to an area of low concentration. This process is known as passive transport, where molecules naturally move to equalize the concentration on both sides.

To understand why, let's first define what diffusion is. Diffusion is the net movement of molecules or particles from an area of higher concentration to an area of lower concentration. It is driven by the random motion of particles and does not require any external energy input.

Now, let's explain the other options mentioned:

a. Movement against a concentration gradient: This would involve moving molecules from an area of low concentration to high concentration. This process would require energy input and is known as active transport, not diffusion.

b. Movement from an area of low concentration to high concentration: Similar to option a, this involves active transport, not diffusion. It would require energy input to move molecules against their concentration gradient.

d. Movement through a permanent barrier: Diffusion can occur through both permeable barriers (allowing substances to pass through) and semi-permeable barriers (allowing only certain substances to pass through). The presence or absence of a permanent barrier does not affect the rate of diffusion.

In conclusion, option c -- movement from an area of high concentration to an area of low concentration -- is the correct answer for when diffusion will take place most rapidly.