The threshold wind velocity is directly proportional to -

Correct option is B

· Threshold Wind Velocity:
· It refers to the minimum wind velocity required to initiate the movement of soil particles, such as in wind erosion or sand transport.
· Relationship with Soil Particle Diameter:
· Threshold wind velocity is directly proportional to the square root of the particle diameter. Larger particles require higher wind velocity for movement due to their greater mass and resistance to displacement.

Where:
· V = Threshold wind velocity
· d = Diameter of soil particles