$16.$ Breeder reactor has a conversion ratio ofunitymore than unityless than unityzeroinfinity$\mathrm{.}17.$ Breeder reactors employ liquid metal coolant because itacts as good moderatorproduces maximum steamtransfers heat from core at a fast ratebreeds neutronsincreases rate of reaction in core$\mathrm{.}18.$ Each fission of U$235$ produces following number of fast neutrons per fission$1$ neutron$1$ neutrons$1-2$ neutrons$2$ neutronsinfinite$\mathrm{.}19.$ Effective moderators are those materials which containlight weight atomsheavy weight atomscritical atomszero weight atomsthere is no such criterion$\mathrm{.}20.$ Electron$-$volt is the unit ofatomic powerenergyvoltageradio activitythere is no such unit.