What is the major difference between a high-speed and a high-torque drill? a. line cord gageb. brush thicknessc. output speedd. chuck type

The Output Speed is generally the main difference. To increase the torque (strength)of the drill, the motor is geared down. The motor in the high speed drill and the high-torque drill may be turning at the same speed but the chucks or bit-holders will be very different. 
Most drills come with two speeds. If the speed is controlled by a gear assembly, then the torque is much higher at the lower speed.

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