Technician a Says That a Driveshaft with U-Joints Speeds Up

Multiple Choice

Technician A says that a driveshaft with U-joints speeds up and slows down once per rotation.Technician B says that to avoid torsional vibrations,the rear U-joint needs to cancel out the non-uniform rotation of the forward U-joint.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B