What are control rods in a nuclear reactor?

The Sun radiates energy continuously and maintains its brightness because:

An atomic bomb consists of two pieces of $_{92}U^{235}$ and a source of:

Pick out the unmatched pair from the following $:-$

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.

Assume that the nuclear binding energy per nucleon $(B/A)$ versus mass number $(A)$ is as shown in the figure. Use this plot to choose the correct choice$(s)$ given below:
$(A)$ Fusion of two nuclei with mass numbers lying in the range of $1 < A < 100$ will release energy.
$(B)$ Fusion of two nuclei with mass numbers lying in the range of $100 < A < 200$ will release energy.
$(C)$ Fission of a nucleus lying in the mass range of $100 < A < 200$ will release energy when broken into two equal fragments.
$(D)$ Fission of a nucleus lying in the mass range of $200 < A < 260$ will release energy when broken into two equal fragments.