See explanation below.
Work Step by Step
a) Control rods of cadmium or boron are good neutron absorbers. Thus they regulate the flux of neutrons to keep the reaction chain in control and prevent the core from overheating. b) The moderator is the substance which flows around the fuel and control rods and slows the neutrons. c) The reflector is a beryllium alloy around the fuel-rod assembly which provides a surface for neutrons that leave the assembly to collide with and therefore, return to the fuel rods.