EMF and PD as work per unit charge Steps:

• X matches the definition of electromotive force (EMF): energy supplied by the battery per unit charge around the full circuit.
• Y matches potential difference (PD): energy lost (work done) per unit charge across a component.
• Both quantities equal work or energy per unit charge, so their SI unit is the volt (J/C).
• Choice C assigns X=EMF, Y=PD, Z=volt, fitting the descriptions and units.

Why C is correct:

• Definitions from circuit theory: EMF = total work by source per unit charge (Kirchhoff's voltage law); PD = work against field per unit charge in component; both measured in volts.

Why the others are wrong:

• A: Assigns correct X and Y but wrong unit (coulomb is charge, not energy/charge).
• B: Switches X and Y (PD ≠ full-circuit battery energy) and wrong unit (coulomb).
• D: Switches X and Y (EMF ≠ component work) despite correct unit.

Final answer: C