Technician a says that gears may be used to apply torque to other rotating parts. technician b says that gears may be used to multiply torque. who is right?

Both technicians are right.

Explanation:

Torque is defined as a rotational force that can be calculated by the formula T= F.d. Being F the force applied to a body to make it rotate and d the distance since the force is applied.  

So technician A is saying that gear can apply a torque to another gear, and that is true because it’s applying a rotational force to the gear next to it, in simple terms  -anytime I make something rotate, I'm generating a torque-. And for technician B, the torque also can vary as a function of the distance of the force applied (size of the gear), so, it can multiply the torque and change the rotation speed.

at positions a, g kinetic energy is maximum.

at position d, potential energy is maximum.