Which of the following is a fusion reaction?

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

$A$ power of $100 \ W$ is produced by the fission of $1 \ kg$ of $^{235}U$. For approximately how long will the energy production continue?

Slowing down of neutrons: In a nuclear reactor,a neutron of high speed (typically $10^{7} \; m s^{-1}$) must be slowed to $10^{3} \; m s^{-1}$ so that it can have a high probability of interacting with isotope $^{235}_{92}U$ and causing it to fission. Show that a neutron can lose most of its kinetic energy in an elastic collision with a light nucleus like deuterium or carbon,which has a mass of only a few times the neutron mass. The material making up the light nuclei,usually heavy water $(D_{2}O)$ or graphite,is called a moderator.

Choose the correct option to complete the net effect of the fusion reaction that occurs in the Sun: $4_1^1H + 2e^- \rightarrow$ . . . . . . $+ 2\nu + 6\gamma +$ . . . . . .

Calculate the power output of a ${}_{92}^{235}U$ reactor, if it takes $30 \, \text{days}$ to consume $2 \, \text{kg}$ of fuel, and if each fission releases $185 \, \text{MeV}$ of usable energy. (Given: Avogadro's number $= 6 \times 10^{23} \, \text{mol}^{-1}$) .......... $\text{MW}$ (in $.3$)