The correct option is B Open disposal of nuclear waste
Radioactivity causes a lot of damage. Hence, preventive measures must be adopted to reduce radioactive pollution.
Testing of nuclear weapons should be done underground and not in the atmosphere. This reduces the radioactive fallout.
When nuclear reactors are used to generate electricity, closed cycle cooling systems should be employed, so that no radiation leakage through coolant takes place.
Radioactive wastes generated by nuclear reactors or from nuclear weapons programme should be disposed in geologically stable underground deep mines to slowly reduce the radioactivity of the wastes.