Technician A says that when the lock-up clutch is engaged on a torque converter,the coupling ratio between the impeller and turbine has to be 1:1.Technician B says at the fluid coupling point in a torque converter,the impeller and turbine must be rotating at exactly the same speed.Who is correct?

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

Technician A is correct because when the lock-up clutch is engaged in a torque converter, it physically connects the engine to the transmission, resulting in a 1:1 coupling ratio between the impeller (connected to the engine) and the turbine (connected to the transmission). Technician B is incorrect because at the fluid coupling point, the impeller and turbine do not have to rotate at exactly the same speed; there is usually some difference in speed to allow for torque multiplication.