Slight rotation of the __ gives a small amount of power steering assistance, which becomes progressively greater as the torsion bar flexes and more assistance is needed. a. Flow-control valve b. Rotary valve c. Pressure relief valve d. Fluid flow valve

## Step 1<br />The problem is about the power steering system in a vehicle. The power steering system is a hydraulic system that helps the driver to by providing assistance. The system works by using a torsion bar, which is a type of spring, to provide power steering assistance.<br /><br />## Step 2<br />The torsion bar is connected to a rotary valve. When the steering wheel is turned, the torsion bar flexes, which causes the rotary valve to rotate slightly. This rotation of the rotary valve provides a small amount of power steering assistance.<br /><br />## Step 3<br />As the torsion bar flexes more, the rotary valve rotates more, providing progressively greater power steering assistance. This is because the more the torsion bar flexes, the more the rotary valve rotates, and the more power steering assistance is provided.