Light Water Reactors (LWR) are nuclear reactors

AWhich use heavy water as a coolant

BWhich use graphite rods as a moderator

CWhich use ordinary water as a moderator ✓ Correct

DWhich use steam as a moderator

Correct answer: (C) Which use ordinary water as a moderator

Explanation

Light water reactors use ordinary water as both moderator and coolant to slow neutrons.

Heavy water as coolant describes pressurised heavy-water reactors, not light water reactors.

Graphite rods as moderator belong to gas-cooled and older graphite reactors.

Steam cannot serve as a moderator, as it is far too sparse to slow neutrons.

Ordinary water is cheap and widely used, making these the most common reactors worldwide.

Enriched uranium fuel is needed because light water absorbs some neutrons.

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