Here's a problem to solve: What is the best way to model the effect of wind on sand dunes?

Among the 4 following options, which is the correct answer?

- A: Pour a bucket a sand through the air.
 
- B: Pour water over a pile of sand.
 
- C: Filter sand through a screen into water.
 
- D: Blow on a pile of sand through a straw.
 