When a spiral spring is stretched by suspending a load on it, the strain produced is called

The correct option is Shearing.

When a load is suspended from a spiral spring, the spring elongates as a whole. However, if we examine the actual deformation occurring within the wire of the spring, the wire does not experience simple longitudinal stretching or compression along its own axis. Instead, the suspended load exerts a torque on the wire, causing it to twist.

This twisting deformation is known as torsion. Under torsion, parallel cross-sections of the wire rotate relative to one another about the wire's longitudinal axis, causing the layers of the material to slide over each other. This change in shape (twisting) without a change in volume is the characteristic feature of shear deformation.

Consequently, the primary strain produced in the material of the wire when a spiral spring is stretched is shearing strain.