The correct answer is C. Air compressors.
Air compressors are machines that use a motor to compress air. The compressed air is then stored in a tank and can be used for a variety of purposes, such as powering tools or inflating tires.
When an air compressor starts up, the motor must overcome the inertia of the moving parts. This requires a higher torque than the rated torque of the motor. The rated torque is the maximum torque that the motor can produce continuously.
The starting torque of an air compressor is typically 2-3 times the rated torque. This means that a 10 horsepower air compressor will have a starting torque of 20-30 horsepower.
The starting torque of an air compressor is important because it determines how quickly the compressor can start up. A compressor with a high starting torque will be able to start up more quickly than a compressor with a low starting torque.
Blowers, conveyors, and centrifugal pumps do not normally need starting torque more than the rated torque. However, there may be some cases where these machines do need more starting torque, such as when they are starting up from a standstill or when they are working against a heavy load.
In general, air compressors require the most starting torque of all the machines listed. This is because air compressors have a large inertia, which must be overcome when the motor starts up.