What type of movement is happening across this membrane?

Question

In the image, the dashed line represents a membrane separating two solutions that is selectively permeable to solutes. The solution on the left is Solution A (50 mg/mL). The solution on the right is Solution B (75 mg/mL). 

 (I can’t insert the image, but Sol. A has 8 dots spread out and on the other side of the dashed line, there is a total of 12 dots, closer together. 

What type of movement, if any,is occurring across the membrane?

a. Active transport

b. Diffusion

c. Osmosis

d. Facilitated diffusion 

Answer 1

Diffusion

The membrane is selectively permeable, presumably to the solute.