This question requires matching constructional features of electrical machines with their respective machine types and the problems they help mitigate.

Analyzing Machine Components and Their Functions

Let's break down the relationships based on standard electrical machine principles:

• Damper Bars (P): These bars are embedded in the rotor poles of Synchronous Machines (U). Their primary function is to prevent Hunting (X), which are oscillations in speed or torque. They also assist in starting the synchronous motor like an induction motor.
• Skewed Rotor Slots (Q): This constructional feature is commonly applied to the rotors of Induction Motors (S). Skewing the rotor slots helps to reduce the tendency for Magnetic Locking (Y) between the stator and rotor teeth, thereby also reducing noise and vibrations.
• Compensation Winding (R): This winding is typically found in DC Machines (V). It is placed in slots in the pole faces and connected in series with the armature winding. Its purpose is to counteract the cross-magnetizing effect of Armature Reaction (Z), improving commutation.

Matching Constructional Features, Machine Types, and Mitigation

Based on the analysis above, the correct pairings are:

• Damper bars (P) are used in Synchronous machines (U) to mitigate Hunting (X). --> P - U - X
• Skewed rotor slots (Q) are used in Induction motors (S) to mitigate Magnetic locking (Y). --> Q - S - Y
• Compensation winding (R) is used in DC machines (V) to mitigate Armature reaction (Z). --> R - V - Z

Therefore, the correct combination representing these relationships is P - U - X, Q - S - Y, R - V - Z.

This detailed breakdown confirms the correct combination among the given options.