Answer: It slows neutrons while absorbing very few.
- A It slows neutrons while absorbing very few
- B It is radioactive and sustains the reaction
- C It has a far lower boiling point than water
- D It strongly absorbs all thermal neutrons
Correct answer: A. It slows neutrons while absorbing very few
Explanation: D<sub>2</sub>O moderates fast neutrons effectively while having a very low neutron-absorption cross-section, letting more neutrons sustain the chain reaction than ordinary water would.
Each water molecule's O-H bonds (covalent, solid) can hydrogen-bond (dashed) to neighbouring molecules, forming an extended network responsible for water's unusually high boiling point and density anomaly.
Concept context
The simplest and most abundant element in the universe. Study its unique position in the periodic table, isotopes (protium, deuterium, tritium), properties of water and hydrogen peroxide, and industrial uses.