Effective moderators are those materials which contain

A. Light weight atoms

B. Heavy weight atoms

C. Critical atoms

D. Zero weight atoms

Answer: Option A

Solution(By Examveda Team)

Moderators are made from materials with light nuclei which do not absorb the neutrons but rather slow them down by a series of collisions.
Carbon in the form of graphite is a material used for moderators as is heavy water which is Deuterium an isotope of Hydrogen with an atomic mass of 2 bonded to Oxygen.