Which of the following is used as a moderator in nuclear reactors? 

1. Plutonium 

2. Cadmium 

3. Heavy water

4. Uranium 

Heavy water is used as a moderator in a nuclear reactor. The function of the moderator is 

1. to control energy released in the reactor

2. to absorb neutrons and stop the chain reaction

3. to cool the reactor

4. to slow down the neutrons to thermal energies

A nuclear decay is expressed as:
$_{6}^{11}\mathrm{C}\rightarrow _{5}^{11}\mathrm{B}+\beta^{+}+\mathrm{X}$
Then the unknown particle $X$ is:
1. neutron 
2. antineutrino
3. proton 
4. neutrino

A nuclear reaction given by; ${ }_{Z}^{A} ~{X} \rightarrow{ }_{Z+1}^{A} {Y}+e^{-}+\bar{v}$ represents:

The mass of ${}_{7}^{15}\mathrm{N}$ is $15.00011$ amu, mass of ${}_{8}^{16}\mathrm{O}$ is $15.99492$ amu and $m_p = 1.00783$ amu. Determine the binding energy of the last proton of ${ }_{8}^{16}\mathrm{O}$.
1. $2.13$ MeV
2. $0.13$ MeV 
3. $10$ MeV 
4. $12.13$ MeV